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It is a 1941 (41) made by Mauser (42) upper that is on top of an unknown lower. I do not think it has the Mauser hump (see the FAQ for side by side pictures) - which means the lower could be DWM from WW1 to around 1934 when Mauser took over production. You can narrow it down to what years made a 'U' suffix, but other than that, it can be hard to tell.
The grips, I assume they are clear with yellow behind them? If actually yellow, then I would say post-war grips, as the GI made ones were made from aircraft Plexiglas and not colored Plexiglas, although who knows where they got it, if no story its just a guess. I have heard of German gun makers making things for GI's or holsters, etc, not usually German POW's as the story
Ed