This article investigates the origins of the British twelve-sided threepenny coin, which entered general circulation in 1937. Having examined the arguments for the coin’s introduction, the article outlines the factors influencing the processes which led to the design of Britain’s first non-circular coin, and considers attitudes both inside and outside the Royal Mint concerning the rival merits of tradition and modernity as they pertained to the British coinage. The article also analyses the dodecagonal threepenny’s position in relation to Edward VIII’s brief reign and George VI’s unexpected accession to the British throne. Finally, the methods used by the Royal Mint both to increase the circulation of this most unusual of coins, and to foster public affection for it, are also explored. Unpopular at the time of its introduction, the coin took several years to gain widespread popular acceptance, coming into its own only during the penny shortage of the Second World War. Whilst the paper focuses on the dodecagonal threepenny its conclusions might be used to think more widely about how people think and feel about money as a physical object, and as an aspect of material and national culture.