Duracell is a well-known brand of battery. AA, AAA, coin buttons – there are heaps of different types.
With its copper top, the ‘Duracell’ nickname is rather inventive as it plays on the fact that both redheads and Duracell batteries have copper-coloured heads.
(Youngsters, if you’re unsure of what these are, as nowadays the good old-fashioned battery is less and less useful, you should still find them in your TV remote.)
See also: ‘carrot top’