<< Its the fed, what else are they gonna give away for completing a survey, real money? I think that mints and maybe some of the fed banks? are clearing houses where banks ship the old money to get replaced. (old money thats falling apart, old issues or whatever, like all the old money with the old designs) The mint then gets takes some of the money they just printed, shreds the old money and then sends the new back to the bank for replacement. I probably have some of the details wrong, but there is a process like that that goes on continually. You probably haven't visited one of the US mints before, they sell bags of the shredded money, or if you are lucky you might get some for free like in this case >>
Money gets shredded at the mint all the time, old bills and what not. To them they're sending out bricks of trash. ; )