A revolving table tool designed to calculate interest rates, 1839.

This revolving interest table, designed by C.M. Riley in 1839, allowed people to easily calculate interest owed on amounts between one and five thousand dollars over a period of one to thirty days or two to twelve months. When European banks raised interest rates on their loans to banks throughout the US, local banks responded by raising interest rates for their borrowers. This cycle contributed to the Panic of 1837.