In Part 1 of this blog I introduced the 37 mm Longines Ultra-Chron models and argued that this particular manifestation of the historic Ultra-Chron line is perhaps the most iconic, with a coherent and subtly distinctive identity that rivals other classics of the era such as the Rolex Datejust, the Universal Geneve Polerouter and the Omega "c-case" Constellation. It's a design that provides a worthy visual signature for Longines' fabulous and innovative in-house 36,000 bph 431 movement (as well as the later 28,800 bph 6651 and 6652 movements, which are basically just the manic 431 on tranquillisers).
While the design of both the case and the dial in these watches is instantly recognisable and entirely consistent throughout their production period, the multitude of case reference numbers applied to what initially appears to be exactly the same style (seven in all, even ignoring the production variant suffixes) is at first a little perplexing. Similarly, while the general style of the dial and hands hardly varies, several dial finishes were produced and there are some subtle differences in the dial furniture and markings that may not be immediately apparent. In this post I aim to demystify the case variations and reference numbers, while in Part 3 I will deal with dial and hand variations. The aim is to provide a basic reference resource for collectors interested in these watches.
The case variants and reference numbers
The seven case references are the 7950, 7951, 7952, 8300, 8301, 8302 and 8348. A good place to start to try to make sense of these is the catalogues of the period. Fortunately, reproductions of two Japanese market catalogues from 1970 and 1972 featuring these watches are available online, and in total they depict six of these seven references.
In the 1970 catalogue (I've cut & pasted the relevant parts together) two of these watches are pictured, both in stainless steel but with different dial finishes. The price list below indicates that the available case materials include "18K YG" (i.e., solid 18K gold, ref: 7950), "SS" (stainless steel, ref: 7951) and "RG" (presumably rolled gold, ref: 7952).
Well, that seems simple enough! The final digit indicates the case material, with "795x" designating this particular case style and the two pictured watches both being examples of ref: 7951.
But let's look now at the 1972 catalogue (again, I've cut & pasted the pictures and text for easy reference):
Here we have two stainless steel models pictured (images 4 and 6), one with a bracelet and one with a strap, and both are now designated with reference 8301 rather than 7951. Then there are rolled gold ("RG") and solid gold ("18K YG") models listed, with references 8302 and 8348 respectively, and a representative gold model pictured (image 5).
This is where it gets confusing. How do the "83xx" cases differ from the "795x" ones? Also, while it makes sense that 8301 is stainless steel and 8302 is rolled gold (with the final digit having the same meaning as in the 795x references), why does the solid gold model have reference 8348 rather than 8300, especially since a quick Google search indicates that ref: 8300 was indeed used for solid gold watches of this style?
It's difficult to see any differences in the case styles of these watches as pictured. The dials differ in the watches featured in the 1972 catalogue in having minute markers (absent in the 1970 catalogue), but case reference numbers (in Longines as well as other brands) usually refer to the metal cases themselves, not to dial and hand variations.
To see how the 8301 (steel) and 8302 (rolled gold) models differ from their 7951 and 7952 predecessors, we need to turn them over to see the sides that aren't shown in the catalogues.
The difference is now apparent. The screw-down case back was redesigned (sometime in 1970, judging by serial numbers) to be opened using a 12-sided ring tool rather than a standard adjustable pin tool as required for the earlier models. It's likely that this would have been a dedicated tool supplied by Longines themselves, thus giving them a little bit more control over who could easily open and service these watches with their specialised high beat movements.
The case numbers of these watches are engraved on the inside surfaces of the case backs. All examples I have seen of the 7951 and 7952 (in person and online) have the "pin opener" style case backs, while all 8301s and 8302s have the 12-sided style.
The strange case of the 8300 (pun intended)
What about the solid gold models, though? Why does the 1972 catalogue list an 8348 18K model rather than an 8300? As I mentioned above, the 8300 exists - in fact, I have two of them myself. They are the watches pictured at the top of this post. One is in yellow gold and the other in rose gold. Longines Heritage Department confirm that the 8300 was produced in both yellow and rose 18K gold (although it's interesting that the Japanese catalogue only lists "18K YG"). Notably, the difference between these two metals is more subtle than is generally seen today. But it's not the metal composition that's relevant to solving this mystery. Here are the case backs of my two 8300s (yellow gold on the left, rose gold on the right):
Unlike the steel and rolled gold versions of the 830x series, these solid gold models retain the older style of screw-down case back. In fact, on the face of it there appears to be no difference whatsoever between the 7950 and 8300 cases. Both of my 8300s date to 1970 (with the serial numbers only 383 apart). However, the 8348 reference does have the newer, 12-sided case back, and the earliest examples of these also seem to date to 1970 (albeit with higher serial numbers).
My theory is that in early 1970, Longines redesigned these watches with 12-sided case backs and changed the case references accordingly from 795x to 830x. However, there must have been some obstacle that delayed production of this style in solid 18K gold. Perhaps the appropriate tools were not yet available, or perhaps Longines already had a stock of unstamped 18K case backs in the older style that needed to be used. So these were simply stamped with the new case back number (8300) that had initially been intended for the 12-sided 18K case backs. Then, later in 1970 when the new 12-sided 18K case backs started to roll off the production lines, they would have needed a new number to distinguish them. This was the reference 8348, which was produced alongside the steel and rolled gold 8301 and 8302 models right up until production ended sometime in the late 1970s.
Variant or production run numbers
The four digit case reference number engraved inside the case back is always accompanied by a one or two digit suffix (following a hyphen). For example, my steel 7591 is, more precisely, a 7591-3. These variant or production run numbers appear to be sequential. The 7951 suffixes go up to 7951-4 at least, while he later 8301 reference, which seems to have been produced right through the 1970s, goes all of the way up to at least 8301-10.
I don't know whether these numbers sometimes, or always, represent subtle changes in the case design, or whether they are usually simply designators of identical but successive production runs. Superficially, there are no obvious differences in most cases. However, there is at least one situation in which this number seems to indicate a particular variant. The very earliest versions of the 795x references produced in 1967 and designated with the suffix "1" (i.e., the 7950-1, 7951-1 and 7952-1) lack the Ultra-Chron logo in the middle of the case back, and are instead engraved with "Longines - waterproof - antimagnetic - shock-absorber - Swiss Made" in a banner surrounding a blank central roundel.
Were all of these watches 37 mm?
All of the examples of these watches I own or have seen online are 37 mm wide excluding the crown, or are described as such - with one puzzling exception. A few years ago, Longines started selling officially refurbished vintage watches through the "Collector's Corner" section of their website. Two of these (now no longer available, although at time of writing still viewable on the website) were the reference 7951. However, while one was described as being 37 mm as expected, the other was, according to Longines, only 35 mm. This supposed size difference was even highlighted in the sizes of the images used in the advertising:
Was this just an error on Longines' part, or was the 7951 (and possibly the 7950 and 7952) really made in two different sizes? It seems very odd that if two sizes of this particular style were produced, they would be designated with exactly the same case reference number. Note that the obvious differences in the dials and hands (including the rectangular date window in the "smaller" watch) are variations that also appear in 37 mm examples (see Part 3). However, I seem to remember that the original version of this advert for the "35 mm" 7951 included an image of the movement in the case, from which it appeared that the case was indeed relatively smaller than the standard 37 mm 7951 case. This image has now mysteriously disappeared.
At this point I remain on the fence (if largely skeptical) about the existence of a 35 mm version of the 7951. I remain open-minded, however, and would very much welcome feedback, especially if you actually have one of these watches in 35 mm!
In Part 3 I will wrap up the discussion with an outline of the dial and hand variants that were produced for these references.
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