Monetary System
Until 1972, British Money was based on the following:
12 Pence = 1 Shilling
20 Shillings = 1 Pound
Early Subsidies and assessments also frequently refer to a Mark. A Mark was the equivalent of two thirds of a Pound so making it worth 13 Shillings and 4 Pence. On this Archive website, the abbreviations Pd (Pound), S (Shilling) d (Pence) and Mk (Mark) are used.