This is what a veteran cop on this website has to say about asking police to check a serial number.
Do not, UNDER ANY CIRCUMSTANCES have any government law enforcement agency do ANYTHING concerning that gun!!!!
If there is anything questionable about it it's YOU that will bite the bullet for it. They will care nothing about how old it is, where you obtained it, etc.
I tell you this as a retired law enforcement command officer.
DON'T DO IT!!!
I'll reiterate this one more time and then I'll keep my peace:
DO NOT PRESENT YOURSELF AT ANY LAW ENFORCEMENT AGENCY AND ASK THEM TO RUN THE SERIAL NUMBER ON THAT GUN!!!!!
You've received some advice here (and I have no doubt that it was given in good faith) stating that if the gun is stolen and you disavow any knowledge of how it came to be that way that you will be sent on your way.
If you're willing to bet your freedom and your future on that, go ahead and put yourself in law enforcement's hands.
But if an old hit comes back on that gun, YOU AND YOU ALONE are the person in possession of it. There is no one else to hang it on.
If the guy who runs that gun is one of those clowns who was at City Market, do you REALLY think you're going to walk out that station a free man?