I went to a local arts market (souvenirs) with my driver. They had sever paintings, sculptures, jewelry, etc. I bought some items and gave the seller a US $20 bill as US currency is widely accepted in the DRC. I went on to the next stand and within a few minutes the seller came up to me. He said that there was a rip in the $20 bill and I would have to give him another since he would not be able to exchange it. The rip was only 1/8 of an inch so it seemed very strange. I took out another $20 bill and compared the two. The magnetic strip was in mine but was not in his although his did have "$20" imprinted repeatedly where the strip should be. A few others around were yelling at the man as this was happening. I kept telling him that it was not the $20 bill that I gave him and eventually walked away. I guess I'll memorize the last few digits in the future in my transactions....or Erin even suggested taking a marker and marking the bills as I pay for things. Lesson learned.....