1. This rule was designed for accountancy calculations in the UK. It was produced around the time that the country converted from pounds, shillings and pence to decimal currency (1971).
2. One of the scales, marked S, allows calculations to be carried out in shillings and pence or for conversion to and from decimal.
3. It also has two scales  for percentage additions (referred to as uplift) and reductions (not shown).
4. On the back there is pair of scales for calculating the number of days or weeks between given dates.
5. The rule also has log-log scales for compound interest calculations.