Penny
From Tardis Wiki, the free Doctor Who reference
The penny was a unit of currency used in the United Kingdom.
Prior to the decimalisation of British money, there were twelve pennies in a shilling and twenty shillings in a pound, meaning that there were 240 pennies in a pound. (TV: Remembrance of the Daleks)
Sarah Jane Smith used a 2p piece to call Sir Colin Thackeray from a public call box. (TV: The Seeds of Doom)
According to Paterson in 1989, the cost of a phone call was 10p. (TV: Survival)
As a child, Amy Pond visited Barry Island where she played the 2p machines. (COMIC: Summer Wholiday)