FACOM 603M Magnetic Tape Unit

There were three initial models with different tape speeds: the FACOM 603A, FACOM 603B and FACOM 603C. Numerous improved models were developed later, such as the FACOM 603D/E which increased recording density to 800RPI, the FACOM 603F/G which provided early 9-track compatibility, and the FACOM 603J/K/M/N which improved recording density to 1600RPI using a new recording system. These models were collectively known as the FACOM 603 Series.