Some really interesting anomalies here: AP - 272 movements Patek - 1 movement in 1956 Vacheron - 806 movements IWC - 217 movements (data missing 1952)
Hmm, it appears that AP made some movements based on Valjoux ebauches (VZSSC/VZSS) for Gubelin in 1954 to celebrate the firm’s 100th anniversary. This may account for some of the AP numbers. I wonder if the IWC numbers could be movements that were made for an outside retailer. https://www.stetzcowatches.com/2020...mars-piguet-built-vz-powered-gubelin-jubilee/
Also, I wonder if the 1956 certification for Patek was the Caliber 34T documented by Fritz von Osterhausen in Wristwatch Chronometers.
@Rumar89 Thank you for taking the time and effort to post this material. The opening paragraphs on the first pages are full of interesting notes. For example, in 1950 the Bureaux seemed quite proud of the fact that about 17% of the watches offered for testing could not pass their tests...this appeared to be offered as proof of the Bureau's stringent requirements that only robust and well-regulated watches could overcome. And yet the Bureaus noted that they had lower requirements for chronometer testing than the Observatories. Other than perhaps a red star on the dial of certain Omegas tested at Teddington or maybe some comments in period Longines advertising, I've never seen any marque make a distinction about where their chronometers were tested. It's also curious that some watches were tested 'avec mention' and some 'sans mention.' Do you think 'avec mention' means that the watch would have received a certificate?
There were two systems, both of which are referred to as chronometer certification, which makes this somewhat confusing: the Observatory Chronometer competitions, which in the Swiss context were held at Neuchâtel and Geneva, and the B.O. certification process, which is the data listed above. The chronometers tested at the Observatory Chronometer competitions were never meant for sale to the general public and very few have come onto the market. These movements were highly regulated, often lacked shock protection, and were re-submitted year after year (after small refinements/improvements) in an attempt to log the best performance in their particular class, which could then be touted in advertising. (I’m not well versed in Omega, so I don’t know if the red star watches were created to highlight Omega’s achievement at Kew, or actually certified there.) Testing took 44 days in Geneva and 45 days at Neuchâtel. Ultimately, this was a competition between manufacturers to see who could produce and regulate their particular movement to the finest tolerances. The B.O. certification process, by contrast, was essentially a mark of quality that demonstrated to a purchaser that the particular watch they were buying performed to a certain standard; “a precision watch, which is regulated in different positions and at different temperatures and which had received a certificate.” Testing here was similar to what took place at the observatories, but was abbreviated, lasting 15 days. With regard to the avec mention and sans mention, the B.O. had two standards of performance. Meeting the higher standard, meant that the movement had especially good results (avec mention). Meeting the lower standard meant the movement was still chronometer certified, but without the higher distinction (sans mention).
On the thread created by @Tony C. - there is an advertisement that mentions a number of points. I believe this is the N number. https://omegaforums.net/threads/lady-luck-delivers-an-early-longines-chronometre.11157/ Reading an actual Bulletin de Marche that I found online, I don't see how that number is calculated. Does anyone know where I might find out how they calculate that?
Seems that we have some clarity with regard to the IWC chronometers. Cal 8521, which was introduced in 1953 according to WatchBase. https://www.thevintageur.com/product/iwc-favre-leuba/