Not in the UK.
The coin you describe is a Gibraltar One Pound coin commemorating the discovery of a Neanderthal skull in 1848. They were the standard issue One Pound coin in Gibraltar for a number of years.
There is a one pound coin and a two pound coin but not a three pound coin.
The British One Pound coin is round.
Stamp collectors are call philatelists. Coin collectors are called numismatics.
Currently, British general circulation currency comes in the following denominations - 1 Penny coin 2 Pence coin 5 Pence coin 10 Pence coin 20 Pence coin 50 Pence coin 1 Pound coin 2 Pound coin 5 Pound note 10 Pound note 20 Pound note 50 Pound note
The 1983 One Pound coin was the year of first issue for the British One Pound coin which replaced the One Pound note. The British One Pound coin is legal tender anywhere in the United Kingdom and some of its dependencies.
vdb
Not enough information to determine the answer here. You will have to consult a knowledgable collector or a catalog. They will be able to look at the stamp and help identify it. Then you can find an estimated catalog value.
Such a coin does not exist. The British One Pound coin was first issued in 1983.
British Pound denominations currently in circulation include - One Pound coin Two Pound coin Five Pound coin (legal tender and often found in circulation) Five Pound note Ten Pound note Twenty Pound note Fifty Pound note
The British One Pound coin, as distinct from the "Sovereign" coin, was introduced in 1983 to replace the Bank of England One Pound note. See the link below.
Swallowing a pound coin could be serious, probably unlike this question.