That's one thing I'm wondering. The USN had the Bureau of Shipping canteen type watch, and IIRC the Russians had French made watches for hardhat divers and a unusual very large watch with a low depth rating for use by divers working on bridges and such in rivers. The Japanese weren't adverse to buying European products if they were deemed superior to home grown, and Japanese officers could carry personal purchase weapons such as European or American handguns. Role made their Oyster case and there were a few competitors. PS Since in the days of the rebreather divers, other than hard hat divers, seldom ventured below 50 feet depth I suspect that many early waterproofed watches could have been used with greater or lesser reliability. There were a few pre WW2 watches housed in separate waterproof cases with view window. and I found one image of a Japanese military watch housed in something like this. It didn't look that resistant to me, but may have originally had a thick rubber gasket.