The Dodecagon is a twelve sided polygon:


While I was searching on the Internet for the dodecagonal shape I found that I could not get hold of one so I decided to make one from two hexagons.  Superimpose two hexagons one over the other and rotate one of them 30° to the left or the right with respect to the other, then join up the points to make your twelve sided shape.  In the days before the decimal currency entered the UK (February 15, 1971) the top coin was, as it would appear, worth 3 old pence and was known affectionately as the “Threepenny Bit” (pronounced “threpp-ney” or if you’re really old fashioned,  “The Thruppenny Bit”.


The new pound coin was introduced in 2017.