I have an opportunity to buy a really nice and clean 41. I am unsure this watch is a WWII vintage. Owner says it was unearthed after the wall fell in 1989. It is remarkable shape and has led to wonder of its true age. Is there a definitive process to determine age. The back is not marked as others I have seen online. This back has 1875 lightly etched on the back. It is nearly invisible. Most watches of that era I have seen are stamped. The watch is missing the top pusher. He would not let me open the back without the proper wrench. I have an appointment with my watchmaker to unscrew the back. I would really like to add this watch to my collection, but do not want to spend money on a non WWII watch. Any advise, thoughts, feedback would be appreciated.