Okay, so the other day I got some change when I bought some stuff at the store. I'm purposely being vague on the place because when I tried to spend some of my change later, I was informed that I had a counterfeit $10 bill. When I compared my bill to one that the cashier had (the one who said it wasn't real) the two bills did look similar enough to be the 'same' but also had enough differences to suspect one to be fake. As it turned out, both were in fact real and not counterfeit.
At least, I HOPE that my bill was real. About a day later I bought some more stuff and used my 'fake' bill without thinking about it. At least by that time I had seen enough on wikipedia to be confident that it was just an older version of the bill and not a real fake. Yes, I did enjoy writing that last sentence.
Hopefully the photos I took show the differences and also obscure the bills enough that they can't be used for making copies. I noticed that not even wikipedia has photos of the bills, which is probably prudent.