The watches were issued to all three branches of the armed forces and were stamped with a different code depending on the branch. The army watches were stamped with W10, I can't remember and don't care what the other branches were stamped with.
My watch came from eBay but from a respected seller (can't remember the name... sorry, but I'm sure someone else will chip in with a likely candidate) and appears perfectly fine to me but is much younger than a watch from the 70s. I guess as these things get older the chances of it being Franken are a bit bigger but maybe not such a problem if it's cobbled together from original bits.