British Threepences have been minted for hundreds of years.
Any collector value would depend on the year and condition of the coin.
Such a coin does not exist. The Threepence was not introduced into the British currency until about 1550.
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There were no British Threepences minted in 1797, bronze or otherwise. Other than Maundy coins, the only Threepences known to have been minted between 1786 and 1833 were the 1792, 1795 and 1800 coins.
A British 1786 Threepence, circulated but still in good condition, might fetch anything from £6 to £40 GBP. A reputable coin dealer will be able to give a more accurate valuation. NOTE - The reverse of these coins is upside down to the obverse. This is normal.
The British Threepence is part of a redundant currency that was withdrawn and demonetised in 1971. It no longer has an exchange rate with other currencies.
Modified coins have no collector value. The ring may have some value.
The Royal Mint produced no British Threepences from 1801 to 1833 inclusive.
The dodecagonal (12 sided) British brass Threepence was first issued in 1937. The Edward VIII coins dated 1937 were never released into circulation and were melted down. Some coins given to vending machine manufacturers for testing purposes, were never returned. The official first release of the brass Threepence was in 1937 with George VI.
The British predecimal Halfpenny, Penny, Threepence and Sixpence did not have an equivalent coin in decimal currency.
The coins are valued between $50 and $100. They coins are not common and the price can vary depending upon its condition.
The 12 sided British Threepence issued from 1937 to 1967 inclusive was made from a nickel-brass alloy. The small silver British Threepence issued from 1920 to 1945 inclusive were made from an alloy of 50% silver, nickel and copper. Although the silver coins were circulated in Britain, they were intended for use in several of the British Colonies.
Modified coins have no collector value. The ring may have some value as a piece of jewellery.