Very Rare! Made of Unobtainium! 3 were made and I own 4! Sale ads

65Val said
For sale: really rare $5 bill. There aren't many around these days. I'll sell it for $100, plus shipping, and don't make me any offers...I wont take 'em....would consider trade for a $50 and 2 -$20's.

I'm interested in your $5 bill. Can you point out what makes yours rare? I just want to be sure I get what I pay for. Educate me. :-D