Casio

Japanese electronics firm that made calculators and from 1974 digital wristwatches. The G-Shock of 1983 was made to withstand drops and shocks.

Kashio Tadao founded the company in Tokyo and first made parts, then an electric calculator with relays. The Kashio brothers made Casio one of the great makers of calculators and electronic instruments.

The Casiotron of 1974 was the company's first digital wristwatch. The F-91W became one of the best-selling watches in the world, and Kikuo Ibe's G-Shock of 1983 became the basis of a whole range of shock-resistant watches.

A module number on the caseback, which identifies the movement and often the decade.

• Clocks and watches
• Casio F-91W
• Casio G-Shock DW-5000C