Astra 600 / German Stamp / Captured enemy equipment certificate

I have acquired a Astra Model 600 that was brought back from WWII. It has the Certificate allowing the gun to be legally brought back to the US ( form # 33 ) from the European Theater. The gun has a 6xx serial number and a WaA1xx number. The frame and slide serial match but I have not taken it apart to find the barrel serial. The gun is in good overall condition and seems to function correctly. There is a lever or button missing on the left side right above the grip cutout. I do not know what its function is. There is one magazine that is marked with the Astra symbol but no serial. I would like to know more about the gun and missing part and what the gun and certificate are valued at. Thanks all.

There were a lot of Astra 600 imported in the 1960's but they latter post-war guns. A real captured gun with the papers should be 2 or 3 times the going price for one of the post-war guns. There is a schematic posted and parts available from Numrich Numrich Gun Parts Corporation