This tool was essential when America was developing and moving west, and the production of wagons and carts was a major industry. Modern equivalents are used today by surveyors to measure distances on the ground.
Was used by blacksmiths and wheelwrights
to measure the circumference of a wooden wagon wheel so that the correct length of iron tire could be made.
The user would roll the wheel along the outer edge of the wagon wheel's felloes (wooden rim) and count the number of rotations.
This one has a pointer and inch markings to help keep a precise count of the distance measured.
The principle on which it functions is foundational to many modern measuring tools.
The wheel is 7-3/4" in diameter and the entire tool is 13" long. Excellent antique condition.