I inherited a Walther PPK 7.65 from my father who fought in the ETO in WW II. He said that he took if from a German officer. The Serial No is 188422 W. It also has a strange marking on the side and the slide. It looks like a small crown over a capital "N". It was fired only once that I know of back in the fifties. It appears to be in excellent condition with no cracks on the plastic grip. The blueing is very good. Can you tell me the history of this gun and what it might be worth and where or how I can sell it?