Steve
Could it be a fake? Check the normal featuers found on a real $1 FRN:
Red and Blue silk threads in the linen paper that can be seen with the
eye or with a magnifying glass. No threads = fake.
Real US notes use an ink that has oil and never dries. Rub it hard on
a white paper and see if the ink smears. If not, it is a fake.
It has the red & blue threads, and the ink does smear onto a sheet of
white paper.
Perhaps you should e-mail "Excelsior" on the Where's George forums as
he is somewhat of an expert on series and variations of FRNs and may
be able to explain what you've got.
Here is a link to one of his recent threads:
http://forums.wheresgeorge.com/showthread.php?t=141583