The Sigma Metalytics Precious Metals Verifier is the single most important authentication tool to enter the precious metals market in the last two decades. It's not cheap — the PMV retails for around $700 and the PMV PRO for about $1,000 — but for anyone with a serious stack of gold or silver, it eliminates the guesswork that keeps collectors up at night. I've used one for over three years and have tested thousands of coins and bars. Here's everything you need to know.
How It Works
The Sigma measures electrical resistivity — how much a material resists the flow of electrical current. Every metal and alloy has a unique resistivity value measured in micro-ohm-centimeters. The device sends a small electromagnetic signal through the coin or bar using a sensor wand and measures the response.
This is fundamentally different from surface-level tests like acid testing or XRF, which only analyse the outermost layer. The Sigma's electromagnetic field penetrates into the body of the coin. The standard small wand penetrates approximately 1–2mm, which is more than enough for coins. The large wand for bars penetrates 3–5mm. This means it can detect a different metal core underneath a plating or cladding layer.
When you place a coin on the sensor, the screen displays a needle on a calibrated scale. The target zone for the selected metal is marked in green. If the needle falls within that zone, the electrical resistivity matches the claimed metal. If it falls outside, something is wrong.
| Metal | Resistivity (μΩ·cm) | Sigma Reading Zone |
|---|---|---|
| Gold (.999) | 2.44 | Green center |
| Silver (.999) | 1.59 | Green center |
| Platinum (.999) | 10.6 | Green center |
| Copper | 1.68 | Slightly right of silver |
| Tungsten | 5.65 | Far right of gold zone |
| Lead | 20.6 | Off scale |
| Steel (varies) | 12–100+ | Off scale |
The Tungsten Question
This is what most people want to know: can the Sigma catch tungsten-filled gold? The answer is yes, and here's why. Tungsten's electrical resistivity is 5.65 micro-ohm-centimeters. Gold's is 2.44. That's a 2.3x difference — massive in terms of electromagnetic measurement. A tungsten core inside a gold shell produces a blended reading that falls well outside the gold target zone, typically to the right of the green band.
I've tested confirmed tungsten-core gold bars on the Sigma. Every single one read outside the acceptable range. The device doesn't tell you it's tungsten specifically — it tells you the reading doesn't match gold, which is all you need. This is the Sigma's killer feature and the primary reason it justifies its price. No amount of clever plating or alloying will fool the electromagnetic penetration.
PMV vs. PMV PRO
Sigma offers two models. The differences matter depending on your collection.
PMV (Original, ~$700): Comes with the small sensor wand suitable for coins and small bars up to about 1 oz. Tests gold, silver, platinum, palladium, copper, and common alloys. The display is analog-style with a needle gauge. Perfectly adequate for most collectors who primarily buy coins.
PMV PRO (~$1,000): Adds a digital display alongside the analog needle, providing a numerical resistivity reading for more precise analysis. The PRO also includes enhanced sensitivity and a wider measurement range. It doesn't come with the large wand — that's sold separately for about $100–$150.
Large wand (sold separately, ~$100–$150): Required for testing bars larger than 1 oz. The standard small wand's electromagnetic field doesn't penetrate deeply enough to characterize a 10 oz bar. The large wand extends penetration to 3–5mm and has a larger contact area for better coupling with flat bar surfaces. If you buy kilo bars or 100 oz bars, you need this.
Accuracy by Product Type
Gold coins (1 oz and fractional): Excellent. The Sigma nails gold coins every time in my experience. Tested against known genuine Gold Eagles, Maple Leafs, Krugerrands, Philharmonics, and Chinese Pandas. All read within the green zone. Known counterfeits — brass fakes, copper-core fakes, and one confirmed tungsten-core fake Krugerrand — all read outside the zone.
Silver coins (1 oz): Excellent. Silver Eagles, Maple Leafs, Philharmonics, Britannias, Kookaburras — all read correctly. Silver-plated copper fakes read outside the zone (copper's resistivity is close to silver but the Sigma can distinguish them). Silver-plated zinc and brass fakes are even easier to catch.
Silver bars (1 oz – 10 oz): Very good with the appropriate wand. One-ounce bars work well with the standard small wand. For 5 oz and 10 oz bars, the large wand is necessary for a reliable reading. I've tested Sunshine Minting, APMEX-branded, and Engelhard bars with consistent results.
Large bars (kilo and 100 oz): Good with caveats. Even the large wand can't penetrate to the center of a 100 oz bar. You're testing the outer few millimeters. A sophisticated fake with a thick genuine silver shell could theoretically pass, though the economics of faking large silver bars are less favorable for counterfeiters than faking gold. For kilo gold bars, the Sigma is still your best non-destructive option short of an assay.
Coins in capsules and slabs: This is a major advantage over every other testing method. The Sigma works through plastic — capsules, flips, and even NGC/PCGS slabs. The electromagnetic signal passes through non-conductive materials without attenuation. You don't need to remove a coin from its protective holder to test it, which preserves graded coin integrity.
Is It Worth the Investment?
My rule of thumb: if you have more than $5,000 in precious metals, or if you regularly buy from secondary market sources (eBay, local sellers, coin shows, estate sales), the Sigma is worth every dollar. Here's the math.
A single fake 1 oz gold coin at today's prices represents a loss of $2,000+. A single fake 1 oz silver coin is a smaller loss, but if you're buying rolls and tubes, a few fakes in a batch can cost you hundreds. The Sigma prevents this loss from ever happening. At $700–$1,000, it pays for itself the first time it catches a counterfeit that your eyes and ears missed.
Beyond financial protection, there's the peace of mind factor. Before I had a Sigma, I'd lie awake wondering about that tube of Silver Eagles I bought from a small dealer at a coin show. Now I test everything when it arrives and sleep well. That psychological benefit is real and has tangible value for anyone who takes their stack seriously.
Comparison With Other Electronic Testers
The Sigma isn't the only electronic precious metals tester on the market, but it's the best for collectors and small dealers. Cheaper options like the Kee Gold Tester ($300–$400) use a different measurement principle and are less reliable for detecting sophisticated fakes, particularly tungsten. The Kee also requires good contact with the bare metal surface, so it doesn't work through holders.
At the other end, professional-grade instruments from Olympus and Bruker (XRF guns) offer elemental analysis but cost $15,000–$50,000 and only test the surface. The Sigma's electromagnetic penetration gives it a unique advantage for the specific threat that keeps precious metals buyers up at night: a genuine gold or silver shell over a cheaper core.
For home use, nothing on the market competes with the Sigma at its price point. It's the right tool for the right job.