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Nippon Calculating Machine Co., Ltd. (Busicom) Model 120-DN Exec Desktop Calculator

The Nippon Calculating Machine Co., Ltd. (NCM) Busicom Exec, Model 120-DN is a desktop AC-powered electronic calculator using a single MOS/LSI (Large Scale Integration) IC manufactured by US chip maker Mostek under contract to Nippon Calculating Machine Co., Ltd.(NCM)

The Mostek MK 6010 Calculator-on-a-Chip (Note NCM Logo on Chip Lid)

The MK 6010 MOS Large Scale IC used in the Busicom Exec 120-DN was the first commercial "Calculator on a Chip". The device was laid out and fabricated by Mostek in the US from a logic design created by NCM.

The Exec 120-DN is a follow-on to the earlier Busicom Junior 120-DM which marked the first use of the MK 6010 calculator chip. The 120-DN is functionally equivalent to the earlier machine, with updates mainly in styling, and a slightly smaller form-factor.

This calcualtor, with a differently-styled keyboard and color scheme, as well as using a slide-switch insead of a thumbwheel switch for selecting the decimal point location, was marketed under the Japanese brand Sanwa as the Precisa M-12, and also by the US company National Cash Register (NCR) as the NCR Model 18-16. Both of these calculators were marketed through the Sanwa and NCR through OEM agreements with Nippon Calculating Machine Co., Ltd. The Old Calculator museum is also interested acquiring in both of these calculators as well as the Busicom Exec 120-DN.