threepenny bit

noun2

1. •
   (historical) A former (pre-decimalisation) British or Irish coin worth three old pennies.

   • All day long he worked, cutting out pennies and shillings and half-crowns and threepenny-bits. — 1934
2. •
   (slang) A woman's breast; a tit.

   • All these skinny modern chicks with their perky threepenny bits do nothing for me. — 1983