Guide

Counterfeit Sovereign Detection: 7 Foolproof Tests (2026)

Approximately 1 in 200 gold sovereigns sold through online auction sites is counterfeit, with the figure rising sharply for sales sourced from outside Europe. Three counterfeit categories dominate: gilt-brass historical forgeries (low value); modern tungsten-cored fakes with correct surface gold; and altered-date examples where common Victorian sovereigns are reworked to mimic six-figure rarities. This guide covers the seven tests that catch all three patterns, in order of cost and certainty.

Last updated: 17 September 2026
In brief. A genuine sovereign: 7.988 g, 22.05 mm, non-magnetic, 17.6 g/cm³ specific gravity, sharp milled edge, no casting seam. Fakes typically fail at least two of these. The five fast tests catch 99% of fakes; specific gravity is essential for tungsten cores; professional slabbing (PCGS / NGC / CGS-UK) is the only certain method for high-value rare-date sovereigns. About 1 in 200 online sovereigns are counterfeit; the rate is essentially zero from Royal Mint, BullionByPost, Atkinsons, Chards or named UK auction houses.
In this guide
  1. How common are fake sovereigns?
  2. Test 1: Weight (catches 70% of fakes)
  3. Test 2: Diameter
  4. Test 3: Magnet test
  5. Test 4: Edge inspection
  6. Test 5: Specific gravity (catches tungsten cores)
  7. Test 6: Ultrasonic / professional thickness gauge
  8. Test 7: Slab + grading service authentication
  9. Altered-date fakes: the high-value pattern
  10. Featured sovereigns on MyCoinage
  11. FAQ

How common are fake sovereigns?

Royal Mint, dealer association, and police data combined suggest counterfeit sovereigns appear in the secondary market at the following approximate rates:

  • Royal Mint direct, BullionByPost, Atkinsons, Chards, Baird & Co, essentially zero. Reputable UK dealers test every coin before resale and are insured against the rare slip.
  • UK auction houses (Baldwin’s, Spink, Noonans), near zero. Catalogued coins are professionally authenticated before listing.
  • eBay UK, strong seller feedback (1,000+ at 99%+), very low (under 1 in 500). Buyer protection via PayPal Goods & Services provides recourse.
  • eBay UK, weak seller feedback or new seller, meaningfully higher (1 in 50 to 1 in 100). The risk is concentrated in this segment.
  • Facebook Marketplace, Gumtree, informal private sale, highest risk. Limited recourse. Avoid for sovereigns above £500 unless you can authenticate in person.
  • Overseas sales (particularly China, Vietnam, Eastern Europe), very high risk. Tungsten-cored fakes originate predominantly from Asian manufacturing operations.

Test 1: Weight (catches 70% of fakes)

A modern sovereign weighs 7.988 g with manufacturing tolerance of approximately ±0.02 g, plus an allowance for circulation wear of up to 0.15 g on heavily-worn 19th-century examples. Acceptance criterion:

  • 7.82 g or above, plausibly genuine. Continue to other tests.
  • 7.70–7.82 g, possibly genuine if heavily worn; further tests essential.
  • Below 7.70 g, almost certainly counterfeit, even allowing for catastrophic wear.

Use a digital jewellery scale that reads to 0.01 g. Kitchen scales reading to 1 g are not precise enough. Many sovereign-fake patterns weigh in the 7.0–7.7 g range, enough to look approximately right but easily caught with a precise scale.

Test 2: Diameter

A modern sovereign measures 22.05 mm in diameter. Manufacturing tolerance is approximately ±0.05 mm; circulation wear typically reduces this by no more than 0.1 mm. Acceptance criterion: 21.95–22.10 mm. Any coin reading 0.2 mm low (21.85 or below) is suspect; 0.5 mm low is almost certainly counterfeit.

Measure using digital callipers (inexpensive). A steel ruler is too imprecise for the ±0.05 mm tolerance.

Test 3: Magnet test

22-carat gold is completely non-magnetic. Bring a strong rare-earth magnet within 5 mm of the coin; any pull or attraction indicates a ferromagnetic core (typically steel). This test catches the cheapest and most common counterfeit category.

Note: a small fraction of counterfeit sovereigns use non-magnetic base metals (brass, copper, lead, tungsten) and pass this test. Use it as a fast first filter, not the only test.

Test 4: Edge inspection

A genuine sovereign has a sharp milled (reeded) edge with uniform parallel grooves and no seam. Common counterfeit failures:

  • Casting seam, a faint line running around the edge perpendicular to the milling, indicating the coin was cast in a two-part mould rather than die-struck.
  • Soft milling, the reeds are rounded or shallow, indicating worn dies or low-pressure striking.
  • Wrong reed count, a genuine modern sovereign has approximately 90–100 reeds per coin; specialist references give the exact count by year. Counterfeits often miss the correct reed count.

Use a 10× jeweller’s loupe for edge inspection. Available for a few pounds; pays for itself many times over.

Test 5: Specific gravity (catches tungsten cores)

The Archimedes water-displacement method. 5 minutes with kitchen equipment.

  1. Weigh the coin dry on a scale that reads to 0.01 g. Record as Wdry.
  2. Suspend the coin from a thin thread tied to the hook of a kitchen balance (or with a sturdy wire loop). Lower it into a glass of room-temperature water until fully submerged but not touching the sides or bottom. Record the new reading as Wwet.
  3. Calculate: SG = Wdry / (Wdry − Wwet).

Genuine 22-carat sovereign: SG = 17.50–17.70 g/cm³ (theoretical 17.6, measurement tolerance). Counterfeit signatures:

  • Brass-cored fake: SG 8–10 g/cm³ (obvious).
  • Lead-cored fake: SG 11–13 g/cm³ (obvious).
  • Tungsten-cored fake: SG 18.5–19.2 g/cm³ (close to gold but detectably high). Pure tungsten is 19.30 vs gold’s 19.32 for the pure element, but a real sovereign averages 17.6 because it’s 22-carat (mixed with copper).

The SG test is the single most powerful kitchen-equipment test and catches every counterfeit type. Combine with weight and magnet and you have approximately 99% detection.

Test 6: Ultrasonic / professional thickness gauge

Bullion dealers and large pawn shops use a Sigma Metalytics Precious Metal Verifier or similar device that measures the acoustic resonance through the coin. Gold and tungsten have different resonance signatures even at similar density, the ultrasonic test catches tungsten cores that pass weight, diameter, magnet and SG tests. Cost is approximately £400–£1,000 for the device, so this isn’t a household test, but a reputable dealer should perform it on any high-value purchase.

Test 7: Slab + grading service authentication

For sovereigns worth £500+, submit to a professional grading service:

  • CGS UK, £15–£25 per coin, 4–6 week turnaround. UK-specialised.
  • PCGS, £25–£50 per coin depending on declared value. The international gold standard for graded coins.
  • NGC, similar to PCGS. UK office in Brentwood.

The slab is tamper-evident; the serial number is verifiable via the grading service’s online database. Slabbed sovereigns also realise 10–20% more at resale than equivalent raw coins, so the authentication fee is often net-positive.

Altered-date fakes: the high-value pattern

The most economically rational counterfeit is not a melted-down fake but an altered common-date coin. Common sovereigns sell for £400 (bullion floor); rare-date sovereigns sell for £5,000–£500,000. Engraving a new date or mintmark on a common coin is a high-margin operation.

The most-targeted dates:

  • 1879 London Mint, no die number, date sometimes engraved over a common 1878 or 1880.
  • 1908 Ottawa (C mintmark), C added to a common London-struck coin.
  • 1820 George III, very rare; sometimes faked from a 1822 or 1823.
  • 1841 Victoria Young Head, date altered from a common 1842 or 1843.
  • 1837 William IV, extremely rare; even one altered example is highly profitable.

Detection requires comparing exact die-feature signatures (specific letter spacing, reverse die polish marks, edge milling characteristics) against published references like the Marsh Gold Sovereign reference. For any sovereign with a five-figure asking price, professional authentication is mandatory not optional.

1 Sovereign - Victoria 1st portrait; Shield
1 Sovereign - Victoria 1st portrait; Shield
1838
up to £26,000
1 Sovereign - Elizabeth II 2nd portrait
1 Sovereign - Elizabeth II 2nd portrait
1974
up to £1,800
½ Sovereign - Victoria 1st portrait
½ Sovereign - Victoria 1st portrait
1838
up to £334
1 Sovereign - George V
1 Sovereign - George V
1911
up to £3,467
1 Sovereign - Edward VII
1 Sovereign - Edward VII
1902
up to £1,300
1 Sovereign - Elizabeth II 1st portrait
1 Sovereign - Elizabeth II 1st portrait
1957
up to £2,400
1 Sovereign - Victoria 1st portrait; St George
1 Sovereign - Victoria 1st portrait; St George
1871
up to £6,250
½ Sovereign - George V
½ Sovereign - George V
1911
up to £1,750

Frequently asked questions

How can I tell if a gold sovereign is real?
Five fast tests catch the vast majority of fakes. (1) Weight: 7.988 g ± 0.05 g on a digital jewellery scale, counterfeits routinely come in 0.1–0.5 g light. (2) Diameter: 22.05 mm. (3) Magnet: 22-carat gold is non-magnetic; any pull = steel-cored fake. (4) Edge: sharp milled edge with no seam from casting. (5) Specific gravity: 17.6 g/cm³ (Archimedes water-displacement test). Together these five tests identify approximately 99% of counterfeits including the tungsten-cored fakes that pass the weight test alone. For high-value rare-date sovereigns, professional authentication via PCGS or NGC is the only certain method.
How common are fake gold sovereigns in the UK?
Counterfeit gold sovereigns are relatively common in the secondary market, particularly via online auction sites and informal sales. Royal Mint, dealer association and police data suggests roughly 1 in 200 sovereigns offered through online auction is counterfeit; the figure rises sharply for sales sourced from outside the UK and Europe. The most common fake patterns are: contemporary 19th-century forgeries (gilt brass, low intrinsic value, sometimes historically interesting); modern Chinese tungsten-cored fakes with correct surface gold but wrong specific gravity; and altered-date examples where a common date is reworked to mimic a rare one. Reputable UK dealers (BullionByPost, Atkinsons, Chards, Royal Mint) carry essentially zero counterfeit risk.
What is a tungsten-cored fake sovereign?
A tungsten-cored fake uses a tungsten core (specific gravity 19.30 g/cm³, very close to gold’s 19.32) wrapped in genuine 22-carat gold of correct surface depth. The coin passes the weight test (because tungsten is similar density to gold) and looks correct (because the outer layer is real gold). The detection methods are: specific gravity test (slightly low because pure tungsten is 19.30 not 19.32, detectable with precise Archimedes equipment); ultrasonic test (different acoustic resonance through tungsten vs gold, the standard professional test); and destructive testing (XRF or drilling, last resort). Tungsten cores are technically sophisticated and almost exclusively appear in 1 oz or larger gold pieces, rare in sovereigns due to the small coin size making the core hard to insert without weight discrepancies.
Can a real sovereign weigh less than 7.988 g?
Yes, through wear. A heavily-worn 19th-century sovereign that has circulated for decades can be 0.05–0.15 g light from edge wear and surface friction. This is not a counterfeit indicator if the rest of the coin is consistent (correct diameter, correct edge, non-magnetic). Mounted, jewellery-modified or holed sovereigns also lose weight without being fakes. The key authentication rule: weight is a necessary but not sufficient test. A coin within 0.2 g of spec is plausibly genuine; a coin more than 0.3 g light is almost certainly counterfeit or significantly damaged.
How do I do a specific gravity test on a sovereign?
Archimedes method, takes 5 minutes with kitchen equipment. (1) Weigh the coin dry on a digital scale. (2) Suspend the coin from a thread tied to a kitchen-balance hook (or a wire loop) and weigh it submerged in water at room temperature. (3) Calculate specific gravity = dry weight / (dry weight - submerged weight). For a 22-carat sovereign the result should be 17.5–17.7 g/cm³ (the theoretical value is 17.6, with measurement tolerance). Tungsten-cored fakes typically read 18.5–19.0 (closer to pure tungsten); brass-cored fakes read 8–10; lead-cored fakes 11–13. The test is destructively conclusive for the gross fakes and quite reliable for tungsten cores.
Where should I buy sovereigns to avoid fakes?
Reputable UK dealers carry essentially zero counterfeit risk: The Royal Mint (the source); BullionByPost; Atkinsons Bullion; Chards; Baird & Co. UK auction houses (Baldwin’s, Spink, Noonans) also carry near-zero risk with their authentication. Higher-risk channels: eBay UK (variable; check feedback and prefer PayPal Goods & Services for buyer protection); Facebook Marketplace (high risk, avoid for sovereigns); pawn shops outside the UK (mixed); informal private sales.
Are old sovereigns easier to fake than modern ones?
In some ways yes. Modern sovereigns (post-2000) incorporate Royal Mint security features: laser-engraved micro-text on the rim, latent images visible only at specific angles, and tincture lines on the reverse design that are extremely fine. These are difficult to reproduce. 19th-century sovereigns lack these features and rely on hand-engraved die work that can be approximated with modern casting techniques, but the edge milling on a Victorian sovereign is also distinctive and difficult to fake convincingly. The hardest-to-fake category is high-grade slabbed sovereigns (PCGS / NGC / CGS-encapsulated), where the tamper-evident slab + serial number lookup provides cryptographically strong authentication.
What is the most common altered-date sovereign fake?
Altered-date fakes take a common Victorian or Edward VII sovereign and rework the date to mimic a rare-date issue worth 10–100× more. The most common targets are: 1879 London Mint (no die number), the date is sometimes engraved over a common 1878 or 1880; 1908 Ottawa Mint sovereign, an “C” mintmark added to a common London-struck coin; 1820 George III, very rare, sometimes faked from a common 1822 or similar; 1841 Victoria Young Head, the date altered from a common 1842 or 1843. Detection requires comparing exact die-feature signatures against published references; for any sovereign with a six-figure realised price, professional authentication is mandatory not optional. See our sovereign mint-marks guide for the genuine Ottawa diagnostics.
How much does professional sovereign authentication cost?
Royal Mint authentication, free, but turnaround can be 4–8 weeks. CGS UK (Coin Grading Service UK), £15–£25 per coin for slab authentication and grading. PCGS, £25–£50 per coin depending on declared value; slab includes grade and certificate. NGC, similar to PCGS. For any sovereign you are about to pay £500+ for, the authentication fee is trivial relative to the loss risk. Slabbed sovereigns also typically realise 10–20% more at later resale than equivalent raw coins, so the fee is often net-positive.

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Reviewed by Connor Jones, Editor. Every MyCoinage guide is fact-checked against realised auction sales before publication.
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