(SM) Few people, even of my age, have seen the silver threepenny bit. I was once given one as change by a bus conductor about 1953 but had to spend it to get home, or walk two miles. I have found another one (1920) in my heap of old coins. They're tiddlers, 5/8" across. The chunky version was around in 1940, as I have one, and two more from the sixties. They're nice. Equivalent in the fifties to about 30p in today's money.
My mum used to have a few for sprinkling in the Christmas pud; although I can't remember ever seeing them in circulation. Here in the Channel Islands we had our own 3d bits. In Guernsey they were nickel silver with a scalloped edge and in Jersey they were round. The latter reason was why we never had 3d slots on our pay-on-answer paypghones.