Those who said "sales tax token" are correct, and those commenting on "mills" or fractions of cents should be awarded extra points.

The best explanation I've found for these is at http://www.taxtoken.org/faq.htm.

Scroll down to the bottom of the page to the heading "Why and how they were used?" and read to learn more.

It's for sequentially numbering/stamping, most likely, cardboard boxes. The ease of advancing the numbers with the gizmo on the handle is the giveaway. Everytime you stamp a box, the number can be advanced... you don't want this to happen if it were being used as a simple price gun.