Patinated, eh? Might be worth the money but finding a part like the slide release may be well....an expensive venture. Tell me about finding old gun parts. I just bought a postwar French .32 pistol. Looked great. Finish good, bore not pitted, I get it home, it will not extract rounds. Tip of the extractor is chipped off clean. Now do you think I am gonna find another extractor? Probably will have to be made from scratch. At least I got the original as a pattern. Unless I set down and make one from a piece of steel with a file, I would have to pay a machinist to make it. How much does that add to the bargain cost? See, even I can get screwed making impulse buys on old guns. At least if I had bought a PPk or something like that, I could probably find an extractor easily. There were tons of these guns made, they are not as old as your Femaru and were made quite late postwar. BUt do you think I can find any parts online or even an exploded view? Buying things like that can burn you unless you know that you can get it fixed, assuming you know the problem before purchase.
Your gun is like your nose, it is just wrong for someone else to pick it for you!