Whether you are sorting a tin of inherited change or bidding on a Victorian florin at a fair, the pleasure of collecting rests on trusting what is in your hand. Most UK coins in circulation are genuine, but fakes turn up often enough that a little routine checking will save you money and disappointment.

Why fakes still slip through

Counterfeiting British coins is not new, and it is rarely sophisticated. In the years before the round pound was retired, surveys suggested that roughly one in thirty £1 coins was a fake — a reminder that even base-metal coins attract forgers who simply want something that passes across a shop counter. The same applies further up the market: gold sovereigns, silver crowns and popular commemorative issues are copied for collectors rather than for the till. Replicas are legal to make and sell, but they must be marked COPY, so an unmarked replica offered as the genuine article is a problem from the outset.

Weigh and measure first

Two inexpensive tools — a digital scale accurate to 0.01g and a plastic calliper — will eliminate most fakes in seconds. Genuine coins are struck to tight tolerances, and forgers rarely manage to match both weight and diameter at the same time.

• 1p: 3.56g, 20.3mm. 2p: 7.12g, 25.9mm.
• 5p: 3.25g, 18.0mm. 10p: 6.50g, 24.5mm.
• 20p: 5.00g, 21.4mm. 50p: 8.00g, 27.3mm.
• Round £1: 9.5g, 22.5mm. £2: 12.00g, 28.4mm.
• Sovereign: 7.988g, 22.05mm. Half sovereign: 3.994g, 19.3mm.

A coin that is a gram light, or a fraction of a millimetre too thick, deserves a closer look before any money changes hands.

Read the rim, edge and lettering

Genuine coins leave the press with a crisp, evenly milled edge and sharp lettering. Cast fakes show a soft, soapy surface, tiny pits, and sometimes a seam where the two halves of a mould met. Hold the milled edge against a bright light: the grooves should be uniform, not wandering, and the rim should be the same depth all the way round. On £2 coins, examine the join between the gold-coloured ring and the silver-coloured centre — the boundary should be clean — and remember that on a genuine coin the design is inverted when you turn it over from left to right. Many forgeries have both sides the same way up. It is also worth comparing the portrait with the date: a 1995 coin should not be carrying a portrait introduced in 1998.

Use a magnet — but know your dates

A magnet is a superb quick filter, provided you know which coins are meant to be magnetic in the first place.

• Bronze 1p and 2p coins (pre-1992) and cupro-nickel 5p to 50p coins: not magnetic. If they leap onto a magnet, be suspicious.
• Copper-plated steel 1p and 2p (from 1992) and nickel-plated steel 5p and 10p (from 2012): mildly magnetic. That is correct, not a fault.
• Nickel-brass £1 and bi-metallic £2 coins: not magnetic at all.
• Gold and silver coins: never magnetic. Strong attraction means base metal underneath, every time.

Colour, sound and surface: the subtler tells

Hold a suspect beside a known genuine example of the same year. Fakes are often too yellow, too orange, or unnaturally pale, and the relief looks flatter than it should. Drop a silver-coloured coin onto a hard surface: genuine cupro-nickel and silver ring with a clear note, while lead or zinc copies give a dull thud. With gold, a fake weighted with tungsten may satisfy the scales but will feel subtly wrong in the hand and sound dead when tapped. Under a loupe, look for tooling marks, blurry legends and the grainy texture left by casting. Genuine wear is smooth and gradual; artificial ageing looks scratched and deliberate.

Buying safely from unfamiliar sellers

• Ask for photographs of the coin sitting on scales, with the weight visible, alongside a ruler.
• Be wary of prices well below the going rate, and of listings that carefully avoid the word "copy".
• Prefer sellers with a clear returns policy, and pay by a method that gives you some protection.
• Meet in person where you can, and take your scale, magnet and loupe with you.
• For anything valuable, buy from established dealers, auction houses or coin fairs, where pieces can be inspected and returned.
• Keep receipts and written descriptions. If a coin later proves false, that paperwork is your best remedy.

None of this demands expert knowledge — just a scale, a magnet, a loupe and the habit of checking before you commit. Do that, and you can enjoy the hunt with real confidence.