This is a Pocket watch movement fitted to a wrist watch case. it's 17Jewel so better than most Omega of that era (I suspect Pre WWII). I can't see to locate any information on this Calibre. Some places list it as 39.1 (using a period instead of a comma), but the movement definitely has a comma engraved in the calibre under the balance wheel. I'd like to service the watch, but I need a mainspring, so identifying the calibre would help (yes I can measure the old one, but it's always nice to have documented info on what should be used). PS. I did locate a seller in CZ selling a Pocket watch with the same movement. but he had no further info. thanks