The dodecagonal brass British Threepence ceased to be legal tender on 31-Aug-1971.
15th February 1971 ?
In Great Britain, the last Threepence coin produced for circulation was minted in 1967. A proof-only Threepence coin was also produced in 1970. Finally, small numbers (usually about 2,000 to 4,000 each year) of silver Threepence coins are produced annually (as they have been for several hundred years) as part of four-coin Maundy sets. The Threepence was initially to be withdrawn and demonetised on the introduction of decimal currency in 1971, but they remained legal tender until about 1974 or 75.
Many British coins were once made of silver. Threepence, Groat, Sixpence, Shilling, Florin, Halfcrown, Double Florin, Crown, Maundy Coins amongst others. If you go back in time far enough, even pennies were silver. From 1947 onwards, no British general circulation coin contains any silver.
None of them are rare or valuable. The coin of which the fewest was minted is the 1936 Threepence of which there were 3,238,670 minted. All of the other years range from 5.8 million to 7.4 million minted.
The British copper Half-Farthing coin was last minted for circulation in 1856 and were demonetised in 1869.
If your asking about the British ten pound note, then it is still in circulation and there are no plans to withdraw it. (February 2009)
When does the old fifty pound note go out of circulation
1983
After the pulmonary circulation is complete, the blood goes back to the heart.
1984
They destroy it. Go figure!
Last issued in 1813