"Pence" is the plural of Penny when referring to a denomination of money.
1 Penny
2 Pence
50 Pence, etc.
You can have 50 Pennies, ie. 50 x 1 Penny coins, or you can have a 50 Pence coin.
The British Pound is sub divided into 100 pennies or pence.
British Coins for example, we have a 1 pence coin, 2 pence, 5 pence, 10 pence, 20 pence and 50 pence.