What is "scleroscope"

A scleroscope is a device used to measure rebound hardness. It consists of a diamond-tipped hammer dropped from a fixed height. The device was invented in the early 1900s. As an improvement on this rough method, the Leeb Rebound Hardness Test, invented in the 1970s, uses the ratio of impact and rebound velocities (as measured by a magnetic inducer) to determine hardness.