First of all, I'm new to Doxa and this is only my second Doxa that I own.
Few days ago I pick up this little watch. From what I have learned on this forum, what I have is a Doxa 300 pre-T, Black Lung, (i.e. first model), but it looks like mine is a very late production of that particular variation.
Case back has a serial number of 6610551, which is the latest one for the Black Lung that I have heard of (ref: https://forums.watchuseek.com/f34/67-...rs-305181.html). The watch has a 'later' version of the hour hand, and the dial is slightly different than the early Black Lungs, however, the configuration is identical to the one that John Vargas posted here: DOXA 300 Black US Divers No "T" (the one on the left).
Here are some scans.
P.S. my other Doxa is a gold 1947 2 reg chrono with swing lugs.