Cool error. It's semi rare/valuable......I bet you wish it didn't have all of those stains. A lot of the error notes are from this era......1963-1995.
This example is similar to yours..... http://www.executivecurrency.com/collections/ProductDetails.php?item=4863
Man, if only it was nicer than it currently holds up. You could make a decent amount of money on it then! Nice find though!