Seiko 6105s were very popular with American GIs in
Vietnam, as the watch had a reputation for ruggedness
and durability in the harsh Vietnamese combat
environment. Although not a "military issue" watch, it was
readily available at the local PX.
This is the "later" of two 6105 series divers made by
Seiko and differs from the first by having a larger,
asymmetrical cushion case and the 6105B movement.
http://scubawatch.org/seiko6105.html
