The Psion Organiser was the brand name of a range of pocket computer

Pocket computer

A pocket computer is a small calculator-sized handheld programmable computer.This specific category of computers existed primarily in the 1980s. Manufacturers included Casio, Hewlett-Packard, Sharp, Tandy/Radio Shack and many more.The programming language was usually BASIC, but some devices...

 developed by the British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 company Psion in the 1980s. The Organiser I (launched in 1984) and Organiser II (launched in 1986) had a characteristic hard plastic sliding cover protecting a 6x6 keyboard with letters arranged alphabetically.

Early Psions are very robust (as witnessed by tech support people who were able to retrieve data from machines run over by cars and even forklift trucks) and they have been sold in very large numbers (about a million).