 To help the Currency Counting staff keep up, the Bank began strap-sorting the $1 to $20 notes.Straps were visually inspected and weighed against a counterweight equal to the paper mass of 100 genuine U.S. notes.Currency straps have even helped catch the culprits in bank robberies, like the Dunbar Armored Robbery in 1997, which happened because one of the culprits decided to pay a real estate broker with a still-strapped bundle of notes.