Nobody invented it. The traditional English coins were originally based on those current in the Dark Ages in western Europe.
The golden coins of the Roman Republic named aureus. The silver coins of the Roman Republic named denarius. The bronze coins of the Roman Republic named sestertius and dupondius. The copper coins of the Roman Republic named as.
Six obols made a drachma. Copper and silver coins.
Pounds, Shillings and Pennies, mostly sterling silver or gold coins, (no paper money).
England is part of the United Kingdom. The currency of the United Kingdom is the Pound Sterling (symbol: £, abbreviation: GBP). The Pound Sterling has coins in denominations of 1p, 2p, 5p, 10p, 20p, 50p, £1 and £2. Banknotes are issued by the Bank of England in denominations of £5, £10, £20 and £50. Wales, Scotland, and Northern Ireland are part of the United Kingdom as well, and also use the GBP.
If you refer to the scrap value of the copper, there is no copper in British "copper" coins these days.
No, copper coins are not typically made of pure copper. Most modern day coins are alloyed with other metals to improve durability and prevent wear and tear. The percentage of copper in coins varies by country and denomination.
In 1892, British coins were made as follows - Pennies, Halfpennies and Farthings were made from bronze. Crowns, Halfcrowns, Florins, Shillings, Sixpences, Threepences and Maundy coins were made from 0.925 sterling silver. Sovereigns and Half-Sovereigns were made from 22 carat gold.
Some coins do have copper in them, depending on the country and denomination. For example, the United States penny is made mostly of copper. However, some modern coins use other metals like nickel, zinc, or aluminum instead of copper.
Assuming you refer to the 1981 British 25 Pence coin (Crown), it is made from a copper-nickel alloy. If you have a sterling silver Proof coin, it will state somewhere on the packaging that the coin is made from sterling silver.
The British silver coinage was degraded from 1919/1920 from sterling silver to 50% silver. All British silver coins from 1919/1920 to 1946 inclusive had a 50% silver content. From 1947 onwards, all circulating British "silver" coins were made from a copper-nickel alloy.
The were no British or Australian coins made from pure copper in 1915. Pennies, Halfpennies and Farthings were made from bronze which was about 97% copper.
In 1900, British "gold" coins were made from 22 carat gold (91.67% gold content). These included the whole range of Sovereign coinage. British "silver" coins were made from sterling silver (92.5% silver content). These included the Crown, Halfcrown, Florin, Shilling, Sixpence and Threepence. British "bronze" coins were made from 95% copper, 4% tin and 1% zinc. These included the Penny, Halfpenny and Farthing.
Circulating US coins were struck in "coin silver" which has more copper in it than sterling silver. The extra copper was needed to make the coins hard enough to not wear out quickly. Please see the Related Question.
The copper content of 20th century British predecimal Pennies, Halfpennies and Farthings varied from 95.5 to 97%. When the use of silver in coins was discontinued after 1946, all British "silver" coins were made from a copper-nickel alloy consisting most commonly of 75% and 25% nickel.
If you intend to "scrape" the copper off for personal gain, most countries have laws concerning the mutilation and disfigurement of their coins.
There were no copper 50 Pence coins minted, they are all made from a copper/nickel alloy giving them a silvery appearance. If your coin is copper coloured, it is either very seriously tarnished or somebody has plated it. Modified coins have no collector value.