Ethical Problem

So here's my latest ethical dilemma.

Somehow or other, I have come into the possession of a counterfeit 100 peso bill (100 pesos is about US$9). I discovered this late the other night when I went to a nearby Oxxo (convenience store chain) and was denied a purchase of a box of Raisin Bran when the clerk, after subjecting my bill to a piece of hi-tech detection equipment, revealed the thing to be a phony.

The guy was quite nice about about it, and patiently showed me how his machine reacted differently to my bill and authenic currency. But as it was the only money I had on me at the time, and so I left without the Raisin Bran.

But even more problematic is that now I've got this phony 100 peso bill to deal with.

It's really quite a nice copy, and in fact, everyone I've showed it to has said that they can't believe it's not real. So if it can't be detected by the naked eye, couldn't I just pass it off on someone who doesn't have a hi-tech counterfeit-bill-detecting machine?

Of course, the people who don't have the technology to detect the bill are likely to be the independent, small-scale entrepreneurs. Conversely, the people to whom I'd love to tender my funny money -- the big chain stores -- are exactly those who can afford the detection equipment.

So what do I do: hang the thing up on my bulleting board as a souvenir, or try to pass it off on mom and pop? After all, they'll most likely be able to pass it along to someone else without problem, right? Right?