July 1963

This is probably the third of at least three Computation Units. Earlier versions appeared in 1951 (unit 123) and 1958 (unit 209). The unit includes:

- linear and logarithmic scales on a paper sheet
- patterns for Napier's Rods
- a slide rule
- a 16-page booklet containing 36 experiments

This unit is an updated edition of unit 209, which contained a longer slide rule and a shorter booklet, but is otherwise identical. The final pages of this unit's booklet contain a description of binary arithmetic, including 6 experiments (exercises), which were not in unit 209.