In order to explain basic arithmetic operations, teachers used a form of the Russian abacus known as the numeral frame. The device was first used in classrooms in France and England and then came to the U.S. It was sometimes sold in combination with a slate.
In the 1870s, inventors proposed variations on the numeral frame that made it suited to posing written problems for a class. The numeral frame also sold in the twentieth century as a child’s toy. Forms of the teaching abacus also have been used to teach about place value and to provide instruction for the blind.
