▋For modern coins in general circulation the most common method of protection from forgeries is the use of bi-metallic coins, made of two metals of different colour, which are difficult to counterfeit at low cost.
The most common way of forging these coins is to change the area that should be a different colour by painting it, however the paint is often easy to scratch off and the coins soon look very crude once worn.
An increasing number of coins are cast from the same composition alloy as the real coin, but have poor reproduction of details such as the milling on the side of the coin and the stamped lettering.
When the euro was introduced into Europe there were initially very few counterfeits, however the number increased massively as time went by. The high and increasing number of fake euro coins in circulation in 2004 led to the creation of a Technical and Scientific Center for the coordination of technical actions to protect euro coins against counterfeiting.
It was estimated that 3.04% of all UK £1 coins in circulation are counterfeit. Between 2002 and 2006 approximately 400,000 counterfeit euro coins were removed from circulation, however “the overall number is very small by historical standards and by comparison to the 69 billion circulating (genuine) euro coins”