Some of the watches I have seen also have an extra number engraved on the back below the ‘AVI’ stamp. One Owner was told by the original watch owner that this is a serial number from the Italian airforce. If this is correct , and I have no reason to doubt it, there are All black AVI’s out there that were purchased by the italian airforce and I assume these were handed to their pilots and/or navigators as tools of the trade and returned after service . The ‘Italian airforce’ pieces are again a combination of ‘digital’ and ‘analog’ watches where the extra number does not seem to follow any serial number range (see list below) where 827818 has number 421 engraved and is a “digital’ version whereas 827833 has number 414 and is a ‘analog’ version.
Some sources also site the French Airforce as origin for the extra 3 digits. 1 Italian forum
http://orologi.forumfree.it/?t=63469678 and 1 french http://forum.chronomania.net/mix_entry.php?id=203319#.UpiMHHdFbwk "the number of French Air Force assignment engraved on the back (52x) Probably this serial was attributed to a military laboratory as cataloging, with subsequent delivery to the various department, For many years this type of watch and follow and 'the 2nd I see with the assignment (at this time and the other' in the network and the owners have pointed out that 'the first time I noticed the attribution of this model)"
How and where these fit into the Military categories for either French or Italian Airforces is currently still unknown and uncertain and needs to be investigated, also proof needs to be provided before this can be accepted as fact
in 1952/1953, the unproven rumors go, Breitling was in intense negotiations w/ the French Airforce and the AVI was developed based on the ref. 765, adapting the 30 minute counter to 15 minutes and adding the 12h bezel – prototypes or a small series were delivered and then the political connections of Breguet/Vixa changed the tender specs to add the flyback functions and Breitling lost the contract. Unsubstantiated, unproven and probably unprovable today, as most corporate documents were not passed on to the new trademark owner, Mr. Schneider. Probably still lying somewhere in a safe