Threepences have never been made from copper.
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.
You do not specify a country or a denomination. Elizabeth II appeared on the coins of many of the 50 plus Commonwealth countries. Assuming you have a British coin (without the country name on it), the coins of copper appearance were made from bronze which is mostly copper. The 12 sided Threepence was made from brass. All of the coins of silver appearance were made from a copper-nickel alloy.
It was traditional to put silver coins into a Christmas pudding.
a coins texture is different because it is much harder and mostly made out of copper and metal.
Except for cents and dollars, modern coins are 75% copper.
Such a coin does not exist. Threepences have never been made from copper.
The coins are valued between $50 and $100. They coins are not common and the price can vary depending upon its condition.
As the name suggests, three Pennies make a Threepence.
If you refer to the scrap value of the copper, there is no copper in British "copper" coins these days.
Pure copper has not been used to make British coins for about 150 years. From 1860, British "copper" coins were made from bronze which consisted mostly of copper varying from 95 to 97% copper. From 1992, British "copper" coins were made from copper plated steel. Ironically, copper is used to make modern "silver" coins (cupro-nickel) consisting usually of 75% copper and 25% nickel.
Copper is not used in British 1 Penny or 2 Pence coin any longer. Since 1992, all British 1 Penny and 2 Pence coins have been made from copper plated steel. The copper plating is merely for visual appeal.
In modern coins, its not. Up until 1991 all 1p coins were struck in bronze (mostly copper) but from 1992-present they are copper plated steel. The reason why they are is because its a continuation of an older practice when a coin's metal was worth about what the coin was worth. For smaller sums, a base metal (usually copper but tin has historically been used for British Coins) is needed because a silver (or gold!) coin would be too small to really use effectively. And small coins are needed for change and small purchases. For slightly larger sums, silver was used because it had a much better weight to value ratio. For example, back in the 1790s a threepence would need to be three ounces of copper to have 3d worth of copper! Silver coins were much smaller (about a gram or two for a 3d). For large sums, gold was used because it had a better value to weight ratio than even silver. Platinum (and Palladium) historically was not used for circulating coins because they weren't valued as much back then. Today platinum is usually more expensive than gold (though not at the moment!) but back in Victorian times, Platinum was used by counterfeiters to put in fake gold coins with a little bit of gold because platinum was much cheaper than gold.