Someone used them to make a pad of $2 bills. Think of a notepad where they are all glued together on the edge and you can tear one sheet off at a time.
Thats what it is. My sister works at a bank and they do it with ones and 2 dollar bills at Christmas time to sell to customers. I would hope one day she could come up with a book of star notes for me but not so far.
The pads are easy to make. I've contemplated making these to sell on ebay, but due to the items being cash, they are a favorite for scammers to prey on.
For making pads, just do a google search for various techniques, but I personally just use White School Glue and clamps from the garage. I cut out thick paper board for a backing and a temporary one to protect the front, then I put paint stirers that I get for free from Home Depot on both side of the edge I'm going to glue. Clamp it together and put three layers of glue on the edge letting it dry each time. when I'm done, it's looks just as professional as the notepads I get from the store and works just fine for peeling one bill off at a time.