In SEIKO, the timepieces belonging to the military watches have been produced from ancient times, and those watches were offered apart from commercial watches. Simultaneously there are so many cases when those who belong to the Department of Defense buy a commercial watch individually for personal use.
In case of SEIKO military watches, there were, for example, the "star mark" printed watch in the dial manufactured from 1935, and the "Anchor mark" and the "Cherry blossom flower mark" printed or stamped on the dial or case back which were manufactured in 1940.
Recently, chronograph watches have been used for military use in British Air Force and a lot of diver's watches have been used in the U.S. Navy or the Maritime Self Defense Force of Japan. Although these are not sold in a general market, when those who belong to the Department of Defense part with the watch, they appear in an antique watch market.
In the case of military watches, it is not officially released on the character which model was offered to where.
Also I couldn’t find an official record concerning about the model of Cal.6138-300X. To the last, it is checked that whether it is a military watch clarifies only when marking is performed on the dial or case back as the main marking of the watch.
Tokunaga
