Dr No[Moderator Omega - Wristscan]
37749
It's a reference 2179, produced in 1945 . . .
. . . or thereabouts, on contract for the American military. The original version of the reference is very rare and almost impossible to find; I've seen only a few examples on the 'net of examples marked solely 2179, without a slash and succeeding digit. Nicolas' is a ref 2179/5, likely produced after the war ended and sold in a PX to a soldier.
Art