amanico[JLC Moderator]
399994
Vintage Blancpain Fifty Fathoms Milspec Rotomatic Incabloc.
The Rotomatic Incabloc mention exists on a few Milspecs, seen in the late 27xx to the early 29xx case number range.
Here are two specimens ( Credit Sothebys and Bonham ).
Number 2860.

Number 2915.
How charming!
Best,
Nicolas