I say find the owners of all that were stolen and return them, take out the good and sell them legally, melt the junk. Oh and I'd be checking up on someone that turned in a valuable weapon for a few bucks, makes no sense to me.
It does happen. One lady turned in a one-of-a-kind gun... and I mean as I recall, the story literally made it out as a only-one-in-the-world to survive relic from WWII she "inherited" when her husband/father passed away. I don't remember the details of the gun or her situation because I ended up more focused on the humanity of the cops who stopped her from turning it in as WAY too valueable to screw her out of for melting down.