If that's an Iver Johnson, then it is a Second Model, made from 1896 to 1908, because it seems to be made for flat spring to power the hammer. (The First Model had a different top catch, and the Third Model used a coil hammer spring). The Second Model was made in the largest numbers and would be the easiest to get parts for, although also the least valuable.
It would be an interesting project to fix, although not much more, IMO. These things were made in huge numbers, and as ApacheCoTodd says, a lot of them are still around. For $10, it's a nice relic.