I was also surprised! Figured I' may find something similar to the type that used to mount on teh front fork and had a "star" wheel that was adjusted close to the spokes, and then you mounted a "pin" on a spoke that turned the star wheel when it came by. I also couldn't believe the price! It seem like the Schwinn odometers cost nearly that back in the late 50's or early 60's! I'm betting the mechanical odometers sold today for that price either aren't real accurate or won't last like the ones I had as a kid.