I once worked on a system for Scotland Yard that allowed a team of data entry staff to transcribe criminal records from paper and microfiche into a database for uploading into the Police National Computer. Included was a routine which would take monetary amounts (usually fines) in pre-decimal format and convert to a decimal equivalent. This worked by taking the each unit (Guineas, pounds, shillings and pence), converting each to pennies, adding them all up and dividing by 240. Luckily I was old enough to have been a teenager on D Day (decimalisation day, not the invasion of Normandy) and could remember how to do it.
A couple of years later I had a call from somebody working for another company - they had been hired by Scotland Yard to write a similar system for different records and had nobody on staff who had even heard of a Guinea, let alone knew that each was worth 252 pence!