The "face value" of a coin is whatever is inscribed on it, hence the term "face value".
The face value of a 10 Pence coin is 10 Pence.
Such a coin does not exist. The British 50 Pence coin was first issued in 1969.
The first British 50 New Pence coin was issued in 1969.
Fifty pence - British coin - was created in 1969.
There was no such coin in Britain. The 50 New Pence coin was introduced in 1969.
There was no 1974 British 25 Pence coin minted.
The British 20 Pence coin was first released in 1982.
There was no 1978 British 25 Pence coin minted.
Such a coin does not exist. The Irish 10 Pence coin was first issued in 1969.
The first British 20 Pence coin was issued in 1982.
There were no British 1975 25 Pence coins issued.
Such a coin does not exist. The British 50 New Pence coin was first issued in 1969. The larger pre-1998 50 Pence coins were withdrawn from circulation and demonetised in 1998. So, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they have little or no value.
Such a coin does not exist. The Eire (Irish) 10 Pence coin was first introduced into the currency in 1969.