This antique iron tool is a spring divider, a precision instrument used by machinists, woodworkers, and engineers for layout work and transferring measurements. Based on the tape measure in your photo, this appears to be a 4-inch or 5-inch model.

Key Features and Uses

Measurement & Layout: It is used to mark off fixed distances on a line or to perform geometric constructions like drawing arcs and circles.

Design: The tool features two sharp "points" (tips) and a spring-loaded bow at the top. A wingnut and screw allow for fine, precise adjustments of the distance between the points.

Historical Context: While widely used in general crafts, similar precision calipers were sometimes repurposed for specialized fields; for example, historical records mention their use in physical anthropology during the 1930s.