Just encountered a comment in an article on Britain's Got Talent that refers to "a dancer who was show[ing] her thrupennie bits to the world."
Thruppence, or the threepenny bit, was, of course, a British coin worth three pence.
And "thrupenny bits" turns out to be Cockney rhyming slang for "tits."
For the curious, the dancer in question was Fabia Cerra, whose performance can be seen in this NSFW photo. (Seems to have lost a pastie.)