Casio 121-F

The Casio 121-F is a continuation of a long line of Casio's 121-series of calculators. The series started in the late 1960's, with the Casio 121-A, a rather primitive 12-digit, four function desktop calculator using Nixie tube displays and utilizing small and medium scale integrated circuit logic. The series was later updated with the debut of the Casio 121-B (also marketed as the Sperry Remington Lektronic.