Hmmm. that's a tough one, I would return it. Why, because I would feel probably too guilty for the tellers who were going to get in crap for the loss, and any employee that would have been canned because of it. It wouldn't cross my mind twice, I would return the coin. Organizations don't forget things like that, if she was smart she would switch 'home' branches' to that location and leverage this throughout her life time, establish a great relationship with the bank and forever be able to negotiate better loan and mortgage rates. Even though the loss would have been a drop in the bucket for them. She got her loan approved because of it, 500$ cash reward, is better than going to jail.