Here's a lovely little thing I came across the yesterday, in a junk shop in Margate. It's a spin-wheel calculator to help you convert decimal currency to old shillings and pence. This is going to be pretty meaningless to anyone who's much under the age of 50.
The UK introduced a decimal currency on Feb 15th, 1971...I remember the confusion and the mental arithmetic that went on almost constantly–I suddenly became much more useful to my parents because I could figure it out quicker than they could.
Clearly this was produced AFTER Feb 15th, though. It only converts from Decimal to old-money and not the other way around, so was probably produced in an attempt to reduce the confusion.