This is Harvey Maranville's first counterfeit U.S. coin detector with a patent date of January 10, 1857 and # 16,390; he patented a second detector in 1860 and a third in 1878.

This is a rocker style detector with a small bottom stand. You place the coin in the holder on the left, and move the slider on the right to the position which identifies the denomination in question. Overall, a very creatively designed and fairly unique counterfeit coin detector from the mid-19th century.