Starting a new thread on this with info based on his serial no.
Meday's Elgin is a 6/0S 15J Class 139 Grade 428 made ca 1927. It's a very typical Elgin wristwatch from that time - close to 350,000 were made in 106 production runs from 1917 to 1932. A nice timepiece, but I still don't see it as a military watch.