closeup of 1 euro coinMany are aware of the many security features found in a currency’s banknotes, such as the watermark, microscopic text, and security strip, but much fewer are familiar with the special features of coins that are aimed at making coin forging impossible. And if you previously thought that coins were not in danger of being counterfeited, think again: the Royal Mint of Great Britain, in fact, just last year unveiled a new design of the British pound coin, created to combat the high rates of pound coin counterfeiting—a design which will roll out in 2017. Here are 4 of the most common security features that you’ll find in today’s coins.

Edge detail

Many of today’s coins are produced to have some sort of decorative edge in order to deter counterfeiting. One of the most common edges of this type is called a reeded edge, as can be found on the U.S. dime, quarter, and half-dollar coins. However, these detailed edges might also feature engraved text, either alone or in addition to reeds along the coin edge. The presidential U.S. dollar coins, for example, feature the text “In God We Trust,” “E Pluribus Unum,” and the year of the coin along the coin edge. Two-euro coins also feature lettering along the edge—in addition to reeds—as do British pound coins.

Sandwiched metals

Though you wouldn’t know at first glance, many coins are actually comprised of a variety of metals, with a smaller metal core “sandwiched” between and surrounded by an exterior of another metal. The current U.S. quarter, for example, is a core of pure copper sandwiched between two layers of cupronickel (75% copper and 25% nickel.)

Bi-metallic makeup

Similarly, some coins of today feature a smaller, inner metal “coin” surrounded by a thick edge of another metal. This feature is perhaps most famously seen on the 1- and 2-euro coins. The 1-euro coin, for example, features a copper-nickel core and a nickel-brass outer edge. The 2-euro coin, meanwhile, features a core of nickel-brass and a thick outer edge of the copper-nickel alloy.

Unique metals

The metals used in coin production themselves can be unique enough that they are rare and extremely difficult to product. The 10, 20 and 50 cent euro coins, for example, are made from a unique alloy called “Nordic gold,” which is a gold-colored copper alloy that is used exclusively in coin making. You’ll also find this unique alloy in in the Swedish 10-krona coin, hence the name. Its composition is 89% copper, 5% aluminium, 5% zinc, and 1% tin