Back when I lived in Colorado and was working in the hotel biz I once got a five dollar tip from a guest. I didn't get tips very often as i wasn't really in a tipped position, so these events were few and far between. The thing was, there was something odd about the five one dollar bills the guy gave me. Frankly, I suspected they might be counterfeit. I put the money in the front desk bank and took out a fiver. In effect, I was passing counterfeit money on a small scale [maybe]. Well, I felt bad about this. The next day I retrieved my funny money from the bank and returned the fiver. So, my next day off I went to the bank and told the bank that I was afraid I'd gotten counterfeit money. Well, the teller looked at it, then went and got the bank manager. She looked at it as well. Then she came over to me and told me these bills had a rough life and had gotten wet but she believed they were real and thanked me for my concern..
She offered my a new fiver and I took it and that's the last I saw of the funny money. I guess I'm not a good paperhanger.