All British 5 Pence coins should have a milled edge.
I do not know about "rare", but it is certainly not how it was intended to be, and if there is one, there may be more.
It would fall into the category of a minting error and may have some value above the usual.
A reputable coin dealer may be able to advise and give a valuation.
The British 20 Pence coin was first released in 1982.
Fifty pence - British coin - was created in 1969.
Twenty pence - British coin - was created in 1982.
Five pence - British coin - was created in 1968.
Ten pence - British coin - was created in 1968.
There was no 1974 British 25 Pence coin minted.
Such a coin does not exist. The British 50 Pence coin was first issued in 1969.
There are 50 British Pence in a British 50p coin.
There was no 1978 British 25 Pence coin minted.
There were no British 1975 25 Pence coins issued.
No. It is a British coin.
British or German