The importance of security features on UK coins

When it comes to the coins jingling in your pocket, the Royal Mint employs a number of sophisticated techniques to ensure each coin is secure and genuine.

But how much do you actually know about the security features that keep your coins safe?

Visible security features

Bi-metallic design

The distinctive bi-metallic design seen in coins like the twelve sided £1 coin and post 1997 £2 coins is not just an aesthetic choice, but an advanced security feature. The combination of two different metals – a nickel-brass outer ring and a cupronickel inner core – increases the complexity of the minting process, making fraud significantly more challenging.

Milled edges and edge lettering

First introduced by the Royal Mint in the 1660s, the complex process of adding milled (grooved) edges or edge lettering to UK coinage not only provides a high degree of visual security, but also makes the coins difficult to counterfeit accurately.

Lenticular features

Special lenticular imaging is another ingenious feature incorporated into some UK coinage. This involves an image that changes appearance when the coin is titled at different angles. The bi-metallic £1 coin, first issued in 2017, showcases this feature beautifully. When tilted, the pound sign (£) changes to the number one (1), creating a dynamic visual effect that is not only mesmerising but also serves as a powerful deterrent against counterfeiters.

Fine engraving, design decisions and micro-lettering

The introduction of new cutting techniques for steel tooling, combined with advancements in computer-aided modelling, has enabled coin designers to incorporate previously unattainable details. These details are as complex as those on a banknote but benefit from being three-dimensional.

Some bi-metallic coin designs extend across both the inner and outer sections of the coin, adding a layer of complexity that helps deter forgery.

Certain coins even include micro-lettering, an advanced design feature that’s hard to produce with consistent quality. For example, the lower inside rims of both the obverse and the reverse of the twelve sided £1 coin feature micro-lettering.

Shape

The introduction of the dodecagonal (twelve sided) £1, first issued in 2017, serves as another security feature. The distinctive shape of the coin makes it much more difficult to counterfeit compared to the previous round pound design.  

Hidden Security Features

Secret messages (Electromagnetic signature)

Some new coins are fitted with a special plating that contains an electromagnetic signature (EMS). When passed through a small electromagnetic field, each coin creates ripples or other disturbances that can be detected and analysed. Different combinations of size and metal cause distinct patterns when the coins are passed through such a field. The distinct pattern of a particular coin is called its ‘electronic signature’.

‘Hidden’ unknown security feature

The Royal Mint announced that the twelve sided £1 coin includes a secret ‘High Security Feature’ which is even more advanced than an Electromagnetic Signature. Details of this feature are top secret, but it’s thought to involve material within the plating layer of the coin which can be detected when electronically scanned by coin-counting or payment machines.

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