This is a single counter from a Hollerith tabulating machine. It has square brass pieces on top and bottom, with a brass mechanism in between. A paper-covered metal dial on top is divided around the edge into 100 equal parts. Two hands are on the face of the dial. Advancing the small hand by 100 (one revolution) advances the large hand by one. Hence the counter can read up to 9,999.
A mark around the center of the dial reads: THE HOLLERITH (/) ELECTRIC TABULATING SYSTEM (/) PATENTED, 1889.