In the Season 1 Episode 8 of Monty Python's Flying Circus, the Army Protection Racket sketch, two cliché Italian mafiosi are trying to blackmail the Colonel into giving them money:
[...] not a single armoured division will get done over for fifteen bob a week.
and then go down to
Twelve and six.
Eight and six...
What does this mean and what purchasing power would this be today?