With the introduction of smaller 5p and 10p coins in 19 respectively, 50p coins became the largest in circulation. This made it easily distinguishable from round coins both by feel and by sight, while its constant breadth allowed it to roll into vending machines. While this design may have been traditional, the shape of the new 50p coin, an equilateral curve heptagon, was revolutionary. The design on the reverse of the 50p coin features a symbol of Britannia that has appeared on our coinage since 1672. In October 1969, 50p coins joined the 5p (shilling) and 10p (florin) coins in circulation, leaving only the three copper coins - to be introduced on 15 February 1971 - to complete the new series of decimal coins.