In the past watches with these markings have generally been thought of as fake, but recent chats with another collector where we swapped info makes me think they could be genuine. My friend sent me these images below.
As can be seen (on the last image, only just!) each are dated M7 for 1967.
Next we go to the A-12 spy plane, produced under the C.I.A. Project Oxcart and used in Operation Black Shield.
First flown on ops 31st May 1967, all pilots are known to have worn Accutron Astronauts in a clear pouch on the back of a glove.
Nothing more was known about these watches until my research discovered these once secret C.I.A. documents below.
As can be seen, a couple of these serial numbers begin with the letter B, as do two watch examples in my first post.
So, as we know these watches were worn by A-12 pilots in 1967-68, the engraved casebacks are dated 1967, and the Bulova serials of some of those watches match in part some of those serials in the documents, I am convinced these watches were worn by A-12 pilots.