Carl Zeiss Jena telescopes are between the most collected and most appreciated from amateur astronomers, also known for their optical excellence. Carl Zeiss Jena (and for some years between the end of WWII to 1990 about also the twin company Carl Zeiss “West”) produced some of the nicest optics like the AS 80/1200, the Telementor, or the APQs. Zeiss items are collected by very high prices all around the world especially in Germany and in the USA. Despite this, there is scarce and widespread information about how to give a date to Zeiss telescopes and accessories, also if each item (most of them) has a progressive serial number, that can help. Many information on Zeiss items and history are conserved in the Zeiss Archive, and many information unfortunately it’s lost or difficult to summarize. This work is a tentative effort to made a summary of the information available at this time, and to start a shared discussion about defining better the knowledge about this matter, that can be useful for people interested in Carl Zeiss Jena history and to Zeiss’s telescope collectors.
Main original sources available: sources for this study have been the following.
- Zeiss “Diarium” (Source: Hans Beck – Walter Stephani).
- Zeiss “Astro 1” Register (Source: Zeiss Archive)
- Zeiss “Astro 2” Register (Source: Zeiss Archive)
- Database of Zeiss Existing Telescopes (DaZET), Lenses and Serials (database produced by Myself in the last 8 years, with sources on the web and personal communication with many Zeiss collectors):
- 1897-1945 Pre-WWII Objectives
- 1897-1945 Pre WWII Telescopes (and Objectives)
- 1897-1945 Aussichtfernrohr Starmor Starmobi Asem Asembi (Astro 1)
- 1929-1976 Telescopes on Astro 1
- 1945-1994 Objectives
Information on sources are summarized in Table1.
Table 1. Sources for Zeiss’s telescope serial number information.
|Source||Kind of information||From Serial||To serial||From (date)||To (date)||Nr.|
|Diarium||Serial of telescope objectives, type of lens, diameter, focal length||26||13.655||1898 ?||1924||–
|Astro 2||Serial of telescope objectives, type of lens, diameter, focal lenght||15.001||38.593||8.3.29||1976 ?||–
|Astro 1||Serial of Asembi, Asem, Aussichtfernrohr, Telescopes, Prisms, Domes, etc.||11.364||50.392||11.10.29||27.10.76||–
|DAZET a. (Pre-WWII Objectives)||Serial numbers of Pre WWII Objectives||606||18503||1945||55|
|Serial numbers of Pre WWII Telescopes||133||17610||1945||93|
|Serial numbers of Asembi, Starmor-Starmobi||33||13911
(Post-WWII Aussichtfernrohr and Telescopes)
|Serial numbers on Telescopes, Terrestrial Telescopes, Domes, Prisms, etc||(14067)
|Serial numbers on Post-WWII Objectives||(18999)
*Number of Entries (as June 2020)
It has to be noted that after 1945 there were two Zeiss divided in the America Occupation Area and in the Russia Occupation Area of Germany, then German Federal Republic and DDR. The sources that are considered here are all to be referred to Jena production, after 1945, I have no information about codification used in Zeiss West telescope production but seems quite clear that Astro 1 and Astro 2 register were used in Jena factory (Carl Zeiss Jena) also after 1945. This has to be further investigated. I know very few objectives from Zeiss Oberkochen, and also on these numerical serials are present. I know a Zeiss Apochromat 150/2232, probably made in ‘70s or before, with Serial Number 6147, owned by a friend, and the 350/4462 of the former Anacapri observatory (Sky and Telescope, May 1965). Obiouvsly this numbers are of a different serial that the one of the “main” series of Carl Zeiss Jena, and probably refferring to a Zeiss West separate register (no information about it at the moment).
All other information in this paper is referred to (DDR) Carl Zeiss Jena or unified Zeiss pre-WWII or post 1989. We can assume, at the moment, that Zeiss Astro Department (unified) ended production of commercial astro-amateur telescopes in late 1995.
Serial on Objectives Dates
First direct Zeiss source is a notebook called “Diarium”. Walter Stephani, that is my source for a copy of the “Diarium” under a request of Mr. Hans Beck, in 2016, has recently (2020) made openly available this source to ATS (Antique Telescope Society) List members. Stephani writes that in his files he had a PDF-copy of the Diarium since many years. During a visit to Jena around the year 2000 he met the former head of the Zeiss Astro Department, Hans Beck, who was already retired at that time (by the way, Mr. Beck celebrated his 90th birthday a few weeks ago). When he left, Mr. Beck mentioned that he had some documents that could be interesting and useful, and he gave to Mr. Stephani a CD. On this CD was the PDF of the Diarium. Some years later Walter Stephani took the trouble to transfer this long list into an Excel spreadsheet, also to be able to search for different aspects in the list. Some years ago Hans Beck and Stephani talked about the Diarium and the Excel version of it. Beck suggested to make the Diarium “Public Domain” after all. Now a copy of the Excel-spreadsheet with all Diarium’s information made by Walter Stephani is published on the ATS (Antique Telescope Society) Forum files, and available for interested people.
Remarks on Diarium (from W. Stephani)
Source: he don’t know if the original Diarium still exists, nor who owns it, nor who has the rights to it. In his knowledge it is not in the archive of the Zeiss company. The Zeiss archive has received my copy of the PDF slide and also the Excel list from him (W. Stephani in letters). Diarium Title: printed title “Diarium” is added with the words “Laufende Objektivnummern” – that means “Sequential lens numbers”. The first 18 pages of the Diarium contain information about the first pieces produced in the Zeiss Astroworkshop, including prisms, (plane?) mirrors, eyepieces and photo objectives. In addition, there is a list of working hours and a Statement of accounts with the Schott glassworks. On p. 7 the first dating “d(en) 6. Juli (18)98″ for ” four planar lenses” is found. The last dating and the end of the more detailed book keeping on p. 18 is May 1900. On the following pages the Diarium is continued as a list. The first column headings are: “Stück/Öffnung/Bildweite/Litt(era)/N(umer)o. Gravi(e)rt-Verkauft/- Pieces/Aperture/Image width/Litt(era)/N(umer)o. engraved-sold/. The last column later is headed with /No. in stock – sold/. From ca. 4300 on it only lists the numbers and occasional details in case of special features. At the beginning of the list, the numbers of the sold lenses were crossed out. This was abandoned later. On the last three pages the Diarium contains the similar information as at the beginning, they apparently are written by the same writers. The list in the Diarium records the lenses with the numbers 26 – 13655. There is no mention of dating in the list. The list ends with the entry “1924”. So Stephani (and myself as well) concludes that the Diarium lists all (most?) Zeiss Astro lenses manufactured up to the end of 1923. The PDF obviously lacks a page with the lens numbers 4516-4673. Last note of W. Stephani is about the Excel list: its goal was to be able to search lenses listed in the Diarium easily. To achieve this, he tried to transfer all information readable in the PDF as accurately as possible into an Excel list. As remarks, he have added time stamps and notes on lenses and mirrors known to him, which may facilitate dating.
From page 1 (cover) to page 18, a series of comments on different items, some date, are listed in non -systematic way. From page 19 as described above a systematic list of consecutive serials starting from n. 26. After page 74 a page is lacking, as above signalled, between serial numbers 4516 and 4673. Page 135 in the pdf is equal to page 137. Page 169-170 are equal to 171-172. Last page with list is page 182. At page 183 there is only the entry “1924”, interpreted as a start of year. Pages 184-186 are notes that start with the word “Ausgang”. There is a “jump” in numeration, numbers are lacking from 8098 to 8897. In a paper of Wolfgang Busch there is a summary of engraving styles of Carl Zeiss Jena objectives: “In the early phase of the Jena Astro department, or about 1897 to 1900, there was, in the objective manufacturing still no mandatory standards for the marking on the cell. This is at # 249 still quasi handwritten and even contains the word Apochromat; for Nr.733 and 819 engraved block letters have been used, but no type of designation, and the focal length has not been specified. Both then become later a standard”.
The “Astro 2” Objective Register
Astro 2 is a register composed by 66 pages, on a pdf file provided under formal agreement from Zeiss Archive. The agreement asks not to made other copies of register nor to let someone other to have a copy. First page is a cover; pages 2 is filled with notes (it seems to be the rear cover?). Page 3 starts with the list, that page is not numbered, but the following is numbered “2” so this is possibly the page “1”. Then the pages follows with consecutive numbers (2-26). Page 27 and 28 are lacking, and the following is numbered “29”. On this page a note says “Seiten 27 und 28 fallh aus”. The series of serial is not interrupted (18.304 at end of page 26, 18.305 at start of page 29). So probably these two pages were lacking before list compilation. First serial number on the list is 15.001, dated 08/03/1929.mPage 30 and page 31 as well are scanned two times, one with a paper note and one without so the text can be read fully. Page 35 is scanned two times, one with a part that is different. After the page numbered 44 the next jump to 47, but the serial number series is consecutive (last 20536 first 20537). From page 53 before the column “Auftrags Nr.” a new column “Zeichn Nr.” appears. Page 54 is scanned two times, one with a note, and another without. Last page is the page numbered 64, last serial number is 38.593.
The last date on the list
Last date on the list is 10.6.1969, on page numbered 61, for serials n. 29.731-29.735. We can try to date following pages using other register Astro 1 (that is dated later, to 1976) as benchmark, considering different information that can be compared (see the next paragraph on Astro 1 for code interpretation). We can use some similarity to found information. On Astro 1 there is a series of three batches of 2.000 Schulfernrohr each: serials 42.565-46564/44.565-46.564/46.565-48.564, dated 27/05/71 the first two and 28/05/71 the third, that have the Aufrag 616 2 2510, 616 2 2513 and 616 2 2516 respectively, that have (all of them) the same “Sach Number” of 16 12 08:003.26. We can observe that these on Astro 1 are dated. Mading a comparaison with Astro 2 allows to found at page 62 the same “triplet” of 2.000 lenses batches, and we found that on two registers these have the same “Order number”, so we can say that are the same, serials are 30.337- 32.336/ 32.337-34.336/ 34.337-36.336 (not dated), that have the Aufrag 616 2 2510, 616 2 2513 and 616 2 2516 respectively; they have (all of them) the same “Sach Number” of 16 12 08:003.26. So also the “Sach Number” is the same, and we can be quite certain that these are the lenses for the order of telescopes that is mentioned above. So also these lenses 30.337-36.336 can be dated in May 1971, as all lenses on Page 62 of Astro 2. Another example is the order n. 616-02-2991 that we can found on “Astro 1”, for 10 Parall. Montierung with serials nr. 50.156-50.165. This order is not dated, but is immediately before another dated 24.10.1975 (and before a long series of items without date, being the previous one available the 14.11.1974 of item numbered 49.552). So we can suppose the order of 10 Parall. Montierung can be made around central month of 1975 (June-September?).
Well, we can find on Astro 2 Register the same order n. 616-02-2991 for 10 Parall. Montierung, but with different serials obviously (38.501-38.519). This two orders on the two different Registers have also the same Such Nr. 16 23 09 : 001-26. So we can infer that these serials on Astro 2 have the same date of previous (so central months of 1975, around). This helps to date the last pages of Astro 2, because this order is on page 63 of Astro 2, where no date can be found.
About this case, it’s unclear to me why this order for mounts is put on both registers, also in Astro 2 that is supposed to be for objectives only. There are other items of this kind in Astro 2, especially in last pages. This mounts so should have two different serial numbers, for reasons that at the moment I can’t understand. Also the writing style and pencil used are very similar, so we can think really that these two entries were made by same person in the same day. A possible confirmation can be a confrontation of some entries in the same page 65 of Astro 2, but earlier, and especially items with Fabrik. Nummer 38.170-38.179, that are 10 AS-Objektiv 150/2250, with Order Number 2805 (and Such. Nr. 16 60 04 : 001-24). They are part of a block of 5 lines with a style of writing and type of pencil different that all other ones.
If we look at Astro 1, we can find that at page 51 we can find a similar style of writing in a series of four lines with serials between 49.264 and 49.348. Between the four batches in question, the first is for “10 Coudé – Refraktor”, that all know that uses AS 150/2250 objectives. This order has number 616 02 2804, one before the order on the other register, and is dated 8.8.1974. So we can think that these two entries on the different registers were associated, being the lenses the ones needed for these instruments. This allow to date the lens serials 38.170-38.179 at August 1974, that is coherent with the previous dating of serials 38.510-38.519, in the same page but after in the list, mentioned above.
Fig. 10 – Astro 1 page 51 (Source: Zeiss Archives)
In same lines with similar graphics and writing there’s also another possible correspondence, that is the one of Astro 2 lens serials (of 40 AS 100/1000) nr. 38.180-38.219 with Order number 2847 and Astro 2 telescope serials (of 30 Amateurfernrohr 100/1000) nr. 49.314-49.343 with Order number 2841, dated 8.4.1974 as well. In this case similarity is less evident, but in my opinion possible. A last annotation is that for both these examples the Such Nr. it is not the same (the real significance of these numbers it’s still unclear to me). All these considerations let to think that the last page of Astro 2 is probably of the same dating of the last of Astro 1, around 1975-1976.
The 40.000 Gap in Objectives list
From information from DAZET, that at moment of writing contains information on about 380 lenses and telescopes, it seems that objective serials with numbers in the range 40.000-49.999 does not exists. A possible hypothesis could be that at the end of use of Astro 2 register, a new register (or database) had been started, jumping to the next round number in tens of thousands, as made in the “Astro 1” register that is mentioned after. This hypothesis is based on the information available at this moment and will change if other evidence about existence of 40k serial lenses will sort out. The very last lens with 30k serial I know is an AS 100/1000 serial n. 38590, that is one of the last batch signed on the Astro 2 register that we can date around 1976 for what I said before. The very first lens with serial after 30k that I know is an AS 200/300 lens with serial n. 50460, that if what written above is correct, could be dated also around 1976 (series re-starting).
Astro 1 Telescope Register
Astro 1 is a register composed by 55 pages in a pdf file provided under formal agreement from Zeiss Archive. The agreement asks not to made other copies of register nor to let someone other to have a copy. First page is a cover; pages 2-4 are filled with notes; page 5 starts with the list, that page is numbered “7”. Then the pages follows with consecutive numbers (7-54) just pages 47 and 48 lacks the corner with number. At the end after page numbered 54 follows two last pages numbered 85 and 86 with a Planetaria list (see after). First serial number on the list is 11364, dated 11.10.1929. List is divided in five columns: “Serial nr.”, ”Number of pieces”, “Description”, a code (“belegh für”), “Date”. Serials, in general, are consecutive numbers. There are some cancellation and some substitution, some notes written on margin, etc… This was a working register in Zeiss factory. Each line of register represents a “batch” of production, with a corresponding internal code (“belegh für”, that means: “Proof of / Evidence of”). Number of pieces is the number of items in the specific batch, and corresponds to the number of serial reserved for the line. Sometimes are only one or few, in some cases a single batch can include 2.000 items (especially after WWII). In the Description column there is the description of telescope or instrument that is made with this serial. “D.F.” in this column probably stays for “DoppelFernrohr” (like the “Asembi” model). Code “belegh für” is probably a production internal number, the significance of this is still under study. In second part of the list there are two different codes, “belegh für” becomes “Auftrag” (that means “Order” or “Job”) and another one Is added “Sach nummer” (“Case Number”, “Thing Number” or “Stuff Number”). The meaning of “Sach nummern” one is undetermined at the moment, the other is the “Order code” and can be linked between the two Registers Astro 1 and Astro 2, as noted above. It has to be noted that from page 40 of the Astro 1 Register a new column it has added, called “Sach Number”. The code referring to this column is also present in many (not all) items from ‘50s, added in “Description” column, but from this point is ordered separately. This “Sach Number” significance at the moment it’s unclear for me, but other code, that from the same page 40 is called “Auftrag” and from page 51 “L.A.” (but appear to be the same code of “belegh für” in previous pages) is probably an Order Code, different for each batch. This code after 1949 constantly is formed by three separate numbers:
- a first code that after 1949 is “616”, with some variation in specific cases (i.e. at serial 17.197 to serial 17.293 corresponding to a 2 m Holspiegel and other big mirrors code is “694”; in this case the number is more complex, 694 9 5151 616 223, maybe they are two codes together, and is repeated for all of them);
- a second one that after 1949 is normally “1” or“2”; with some variation in specific cases (i.e. at serial 1797 above mentioned is “9”);
- and a third of four numbers, that is changing for each batch, and that is tendentially increasing (with some variations).
Probably, in general, first number “616” is the number of unit of production (Zeiss Astro Dept?), “1” or “2” are probably sub-units inside the Dept. ant the third number is the specific number of each order. About the other code “Sach Number” all remains to be understood. I observe that in some case is the same for different batches: as for three big consecutive batches of 2.000 Schulfernrohr with serials 42.565-46564/44.565-46.564/46.565-48.564, dated 27/05/71 the first two and 28/05/71 the third, that have the Aufrag 616 2 2513, 616 2 2513 and 616 2 2516 respectively, that have (all of them) the same “Sach Number” of 16 12 08:003.26. Date probably means the date of start of the production of the specific order (batch); it is not a final date of delivering of the item, that probably is very much variable. If the order is for one single lens the production time is limited, but for orders with 2.000 items or for very large telescopes obviously this can ask months or years. So this is just a general reference on age of the telescope. This system was choosen by Zeiss probably because this allows to have a certain serial number for each item from start of production. It’s interesting that some item has not a serial engraved on itself (like some telescopes or lenses), but if this reasoning is correct they should have in any case an assigned serial number.
Type of item listed
On Astro 1 cover title tells “Astro” with an added nr. “1” and follows with “Fabrikations Nr. fur: Aussichtfernohr, Kamera, Urgan, Spiegel u ___, [a word that is not readable, cancelled], Planetarium (?) Kuppeln”. In the list we can find this kind of material and other like prisms, especially before WWII. After WWII in Astro 1 are listed Schulfernor and Cassegrain-Meniscas telescopes, as well.
Annotations on registry
Astro 1 Telescope Register is introduced by a series of draft notes written on small paper pieces, some of them very interesting to understand better the way in wich Zeiss’s technicians numbered items. On note says “Alle Fabrikationsmummern warden durch L-V gegeben” that means “All manufacturing numbers are given by L-V”. The meaning of this note has to be cleared, as now. Another note is “Fabrikationsnummern fur Starmor, Starmobi und Asiola fortlaufend ab Nr. 1922” that means “Manufacturing numbers for Starmor, Starmobi and Asiola consecutively from no. 1922”. This information is corresponding to the observed numbers on Starmor, Starmobi and Asiola on the Astro 1 list. A third note is “Asem erhalt keine Fabr. Nummer, weil die Nummer von Prismen-Umkehrsatz als Fabr. Nr. gilt” that means about “Asem doesn’t have Fabrication numbers, also if the number on prism is the fabrication number assigned”. I observed that this rule is valid for all terrestrial instruments that are listed on Astro 1 list, that has not the F.N. on the focuser, as the telescope have, but on the inversion prism. So this number is corresponding to the F.N. of the whole instrument.
The 22.278-35.000 Gap
In Astro 1 after the Serial 22.277 dated 4.2.1959 a double line signs an interruption. List re-start with an annotation “neue # Gruppe”, after wich the list re-start with number 35.001, dated 13.2.1959. It seems to, considering that the dates of the two above mentioned serials are very near, that there is a gap in serials from number 22.278 to number 35.000.
The last date on the list
Astro 1 list terms with serial numbers 50.393-50.395, corresponding to three KFPI3, produced from 3.4.1990. This is a late addition to the list, because the previous entry is dated 27.7.1976, corresponding to serials 50.373-50.392, of a batch of 20 Amateurfernrohr 100/1000. We can use this last date and the previous to date the serials on the other list (Astro 2, Objectives), using a confrontation between writing styles and other elements (see paragraph on Astro 2).
What happened to telescope numeration after “Asto 1”
Altough the series of objective Fabrikationsnummern followed in the years after 1974, and we suppose in chronological order, It’s not very clear what happened in telescope numeration after these numbers. It seems that the rule to made numbers also for OTAS followed, but this is uncertain at this stage. There are some numbered telescopes in the ‘80s, with serials on tubes and mounts, like one of first APQ 100/1000 Objective n. 96025 associated with mount Nr. 86280, and Nr. 85015 on OTA, sold in 2014 in an auction and then on a famous site. I’m also aware of a PaMont II with serial 97.486. Hard to say if the serial sequence for items like mounts in ‘80s – ’90s is the same of the one of the objectives.
Very interesting is documentation about APQ objective Nr. 98.130, an APQ 100/1000. This seems to be at now the highest Zeiss objective serial number ever. I have access of a copy of Zeiss test report for this lens, that is dated 24/08/1993. This telescope has also a number typed (engraved?) on the tube, that is the same number 98.130. A strange thing it’s that despite this is a very recent APQ, the label is marked “Carl Zeiss Jena” with the old logo (it’s its original lens?).
This lens has been sold on a famous commercial site in 2016. On the same site in 2020 an APQ 100/640 has been sold, with lens serial Nr. 97819, but on the tube the serial Nr. 98207, that so seems to be the absolute number higher in the series of OTAs. Unfortunately I haven’t for this lens the Zeiss test.
A third one, has the objective n. 97109 and the number on serial 98159.
A possible consideration about this is that can lead to two hypothesis:
- Zeiss used to match a lens number with the same number on the OTA, but in some moment in time objective has been exchanged with another one (in the case of 97819 lens and 98207 tube and 97209 lens and 98159 tube it doesn’t match);
- Zeiss do not used to match objective and OTA if not sometimes, and so all the above telescopes are in the original configuration as sort by Zeiss factory (and there are two different lists for tubes and lenses?).
Some other cases has to be verified before to make a conclusion on this. I put on a table the APQ lens serials for those that have a known test report (just 12 objectives). It seems to be no correlation between the date of report and the serial number. It’s interesting that the second earlier (96996) and the last (98130) have about the same date for test report. What does it mean? That all APQs were produced in a single batch and sold in the following years? Note tat the latest seems to be dated 2003, and many are after late 1995, when it is known that Zeiss Astro Department closed.
Table 2 – Serials and Test Report dating of Zeiss APQs.
|Serial Number||Data Zeiss test report|
So some final consideration about the Zeiss test report dating. A test report can be made if a lens is already existing, obviously, so the test report can be the witness that at that date the objective was existing. Thus, I can say that the lens Nr. 98130 above mentioned was made certainly before 24 August 1993. But they are lenses with a lower serial number, like the 97695, that (if – assumption – lens serial are consecutive) has to be made also before 14 August 1993: but its serial report is dated 23.09.1998. So 1993 is before 1998, but long before…
What I can think is that:
- Test reports were made by Zeiss at the moment of sale of lens, and not at the moment of production; OR
- Serial numbers are not ordered consecutively in time.
At the moment I’m more of the opinion that hypothesis 1) is correct, but probably more information is needed. Another very interesting observation is that in my database between Nr. 96996 to Nr. 98130 there are no other kind of objectives, APQs only (32 of them I know)! The only exception to this rule is the above mentioned PaMont n. 97486 (but I can’t be certain that the numeration is the same, or if another list of items different from objectives does exist). So this can lead to the (working) conclusion that all serial from Nr. 96996 to Nr. 98130 are used for APQ lenses? It could mean that the total of APQ produced could be around 1.134. This figure is a bit higher than the estimate that some expert published on an American forum. But has to be noted that some APQ has been produced long before, it has written in the past on Achromat.de that an APQ with serial n. 79.315 does exist (maybe the very first series of APQ 100/1000 in 1986?), and I have other entries for APQs between serial Nr. 95973 and Nr. 96112. Between Nr. 96112 and Nr. 96996 other kind of lenses (i.e. AS) are present. If after Nr. 96996 I found all on 32 lenses as APQ by chance, I’m lucky! But it can’t be excluded.
The Planetaria list
At the end of the Astro 1 Register there is a list of serials used for Planetaria, from serial n. 55 (Year 1949) to serial n. 388 (Year 1990).
Summary: Series of serials
Using the above mentioned information, we can distinguish the following separate continuous series of serial numbers in Zeiss telescopes, related to the available original information:
- Serials of Objectives
- Lacking period: 1897-1899 ? (Serials 1-25)
- Reference source: Diarium. Period covered: 1897 ? – 1923 ? (Serials 26-13.655);
- Lacking period: 1924-1929 (Serials 13.656-15.000); (information on single telescopes from DAZET A.
- Reference source: Astro 2 Register. Period covered: 1929-1974 ca. (Serials 001-38.593)
- Lacking period: 1975-1995 (Serials 38.594-98.130 or higher). Information on single telescope from DAZET E.
- Serial of Telescopes, Terrestrial telescopes, accessories, etc…
- Lacking period: 1897 (or before)- 1929 (Serials 1-11.362)
- Reference Source: Astro 1. Period covered: 1929-1976 ca. (Serials 11.363-50.392)
- Lacking period: 1976-1995
- Other serial series:
- Asembi after WWII (from ‘70s) apparently follow a different serial numeration (probably the binocular series, with six-entries serials).
Picture credits: information in the reference archive used for this paper are a collection of the cited sources and many widespread others on the web. Main source of data and pictures are www.astromart.com, www.cloudynights.com and www.apm-telescopes.de (both online edition and archived copies in www.archive.org), of Markus Ludes, that is the main seller of old Zeiss telescopes in the world. Copies of old Zeiss registrers are used under permission of Zeiss Archive. I thank Walter Stephani and Dan Schechter for text revision and many Zeiss passionate collectors for exchange of ideas during time, especially Bob Trotter of Western Australia.
 Busch W., Zur Entwicklung der Fernorohrapochromate im Zeisswerk. Paulys zweilinsiger Apochromat “A” – Anfang und Ende. Jenaer Jahrbuch zur Technik – und Industriegeschichte Band 17 (2014), S. 125-139.