It was still legal tender when I was young. When they started to relax rationing in the UK after World War 2, I could buy little liquorice sticks — about 4 inches (10 cm) long and about half the thickness of a pencil — for a farthing each. But the shop wouldn't allow me to buy more then four of them

I've never heard that one (about the spy) but I can well believe that it's true. You really need to live in a country and speak their language with reasonable fluency before you understand all the terms in common use. Staying with the currency, the coins in common use were:—
1/2d — halfpenny, or ha'penny (pronounced hayp-nee)
1d — penny (plural usually "pence" rather than pennies)
3d — threepenny piece or threepence or more commonly threepenny bit (the "ee" pronounced with a short e as in "pen" or occcasionally with a short u as in "up"
6d — sixpenny bit or sixpence, or most commonly tanner
1s — shilling, or most commonly bob (written as 1/0 or 1/-)
2s — florin, but almost universally called either two bob, or two shilling piece ("two shillings" almost always referred to the amount of money rather than the specific coin. As with 1s, written as 2/0 or 2/-)
2/6 — half crown or half a crown (never anything else)
5s — crown (Never called anything else; vanishingly rare in actual commerce. More usually present as commemoration issues to celebrate special events, e.g. coronations etc. I had one commemorating the death of Winston Churchill in 1965)