Here is a misprint that can go unnoticed for years. As you can see, the note below has two different serial numbers. These misprints are actually fairly rare. However, due to their mundane nature, they aren't terribly valuable.
A misprint with a mismatched serial number will probably be worth around $500 in uncirculated condition. Mismatched serial number errors on circulated issues can be bought for less than $200.
We are certainly interested in purchasing all mismatched serial errors. Our offer will be based on the number of digits misprinted and the condition of the bill. Send us a picture of your misprint firstname.lastname@example.org