Reviews of 13 electronic gold testers

Last updated: October 1, 2025

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This article reviews several electronic gold testers, including how they compare with using chemical (acid) testers.

SUMMARY
KEE (MODEL M-509GM) £349.00
GemOro models AGT1, AGT2, AGT3.
MIZAR M24
HOW THEY ALL COMPARE

SUMMARY

KEE. This wins on being the easiest to use, for consistent reading, and for accuracy. You should (with very careful calibration) get a good reading all the way up to 24ct. Scroll down to see a review.

The Auracle ANALYZER. has the same electronics (microchip) as the KEE tester, giving an almost instant result, just like the KEE, but on an LED scale rather than an analogue meter. And there's a digital display telling you what to do, especially useful for calibration.

Auracle PRO (available early October) is an upgraded version of the AGT3 tester, fully digital, one-touch calibration and (unlike the previous AGT models) it's CE-approved - they say it's much more stable than any of the old models.

ELECTRONIC TESTERS V. ACIDS. The electronic testers we sell do not use acid. Accuracy. If you want to test high-carat accurately (e.g. to see the difference between 21ct, 22ct and 23ct) acids are more accurate. Ease-of-use. On balance, the electronic testers are easier but even the acids are 'easy to use' once you've tested a dozen items and have got the hang of it. Consumables. A bottle of acid needs replacing when used up, but so too does the pen-probe of an electronic tester. An analogy: a pen-probe is the equivalent of an all-in-one ink cartridge (one probe for all carats); bottles of acid are the equivalent of individual ink cartridges. Reliability. Although the latest testers are reliable, any electronic device can break down. If it breaks down after the one-year guarantee, the best option is to throw it away and buy a new one. A bottle of acid can't break down, you use up the acid, you buy a new bottle.

KEE (MODEL M-509GM) £349.00

Click here to buy.
(or click here if you already have one, and need a replacement pen-probe)

ACCURACY

You should (with careful calibration) get a reading to the nearest 1ct all the way up to 24ct.

PROS

good price for a tester that works well
the easiest to use. You still have to read the instruction manual but apart from calibrating (and cleaning the sample) it's self-explanatory, you won't have to keep referring to the instruction manual to find out about menus and error messages
simple design, fast response, the needle on the meter shoots up to the carat marked on the dial in a couple of secondds.
accurate when testing high carats (needs careful calibration with both and 18ct and a 22ct sample) - for instance for distinguishing 20ct to 24ct 'Asian' gold.
good size for carrying around (supplied with a pouch that takes the tester and all the accessories)
extra set of leads for testing large itemst hat won't fit on the test plate,

CONS

no option for a mains power supply, it's battery-only, though the battery should last many months...unless you leave it switched on (there's no LOW BAT indicator).
not reliable for testing platinum, the best you can say of a "platinum" reading is, 'It might be platinum or Palladium".

WHY DOES IT HAVE AN ANALOGE METER AND NOT A DIGITAL DISPLAY?

If you think anything with a digital display must be more accurate than an old-fashioned mechanical meter - think again. There is no connection between the type of display (digital or analogue) and accuracy. A digital display will give you a reading to the nearest 1ct, but it is not necessarily accurate.

CONCLUSION

This is definitely my favourite, we've been selling this since 2018 and have sold a few thousand, and nobody who has read the instructions complains that they don't understand how to use it. It is also the most reliable, with well-less than 1% 'returns' which is quite remarkable.

Download the instruction manual.

GemOro models AGT1, AGT2, AGT3.

Although we stopped selling these a few years ago, and this series is no longer manufactured, we can still get replacement pen-probes:

You can also buy a replacement probes.

Please note, this section is for information only, these models are no longer available.

Not all AGT1s are the same.

AGT1 (original model)

Quite OK once you've got the 'feel' for how the lights shoot up, then keep going up, then slowly go down, and usually settle on a reading...but many people try for a few minutes then give up. Shop staff who don't get proper training and don't have time to 'get the feel' and are under pressure in a busy shop - they will have no chance of getting a meaningful reading.

Each time you switch it on you must calibrate against the 14ct calibration sample, sometimes it doesn't work and you have to calibrate it 2 or 3 times, then you must 'charge' the probe by carrying out a few 'dummy' tests before getting a reliable reading, and all of this takes a couple of minutes. Every few days (if you're unlucky) or every few weeks (if you're lucky) it has a nervous breakdown and won't work at all, it is not 'broken', you can fix it by calibrating it 6 or 7 times in succession, it's not difficult to do but it is frustrating, especially if you have a queue of customers. Not very accurate at testing above 18ct.

AGT1 Plus

Compared with the AGT1 (original) above, calibration usually works first time, it has nervous breakdowns less often, it 'feels' nicer to use (more responsive). You still have to 'charge' the probe by carrying out a few 'dummy' tests before getting a reliable reading. It's not as frustrating to use as the original AGT1 but there will still be times when calibration doesn't work the first time and you have to calibrate it 3 or 4 or 5 times in succession. You still need to spend time 'getting the feel' of the readings.

AGT1 Deluxe

The full name given by the manufacturer's is AGT1 PLUS DELUXE

The supplier says that the electronics were re-designed and you don't have to 'charge' the probe before use...but they also say that you should charge the probe anyway. We couldn't find any difference between this and the earlier models as regards operation.

CONCLUSION: AGT1s are not, "Simple to use" and also, they are long-since discontinued. If you are happy with their idiosyncrasies and are prepared to spend time and effort 'getting the feel' - then perhaps try finding a secondhand one.

AGT2

This consisted of a probe, a testing plate, a box of electronics (not shown in the manufacturers pictures), connecting leads and a large fitted case. You connected it to your phone. It was discontinued in 2018. Then they discontinued the app. - that meant if you updated the operating system on your phone or got a new phone, you could no longer use it. Although this is all 'ancient history' it's worth bearing in mind in case you are offered a secondhand one.

AGT3

Fully digital version, new sleek design, one-touch calibration,

MIZAR M24

This is the best of the MIZAR models...but we no longer sell this.

ACCURACY. Plus or minus one light, e.g. if it reads 14ct it might be 12ct or it might be 16ct but not this accurate above 18ct. OK if you want to know if an item is "low carat" or, possibly, "high carat" - otherwise, fairly useless.

PROS. very cheap; - very simple, a light for each carat; Mizar make a few models, this is by far the best of them

CONS. not accurate.; the acid contact fluid will dissolve the sensor if it is not cleaned meticulously after every use; you need good eyesight and a steady hand to place the test-item into the tiny well that you fill with acid; you can only test tiny items; no carrying case, no mains power option, no way of calibrating it.

CONCLUSION. Not the best, but certainly the cheapest.

HOW THEY ALL COMPARE

How do they compare for accuracy?

Most scrap-buying in the UK involves 9ct gold, occasionally 14ct or 18ct, rarely 22ct. However, there is also a market for 'Asian gold' and traders need to know if an item is 20ct, 21ct, 22ct or 23ct. Most of these electronic simply aren't accurate enough to do this, the only one I would recommend is the Kee tester (if you calibrate it very carefully it is accurate to the nearest 1ct). Other than the Kee tester, if you want to test high carat gold, use acids, they are more accurate.

M24: don't even think that you can get a meaningful reading on high carat gold. It might be OK if all you want to know is, "It's gold, probably a low carat" or "It's gold, it might be about 14ct but we don't really know" or "It's gold, it might be high-carat".

AGT1: quite accurate for testing low carat (e.g. 9ct to 14ct); for high carat it is accurate to plus-or-minus about 2ct. 'Reading' the lights is a matter of judgment.

AGT3: quite accurate for testing low carat (e.g. 9ct to 14ct) but for high carat it is only accurate to about plus-or-minus about 2ct (even though the display will always give reading to the nearest 1ct).

Kee: the most accurate for all carats (including high carat) providing you calibrate it very carefully.

If you want to test more accurately than listed above, then there is no point in buying any of the low-cost electronic testers (listed above), either use acids or splash out on a £12,000.00 XRF tester.

How do they compare for size of the machine?

The models that connect to a phone are the smallest [now discontinued] but not quite as small as the photographs suggest, you also have the connecting leads and a box of electronics. After that, the M24 is the smallest (there is no carrying case)followed by the Kee (in its carrying pouch). The Gemoro (AGT models) are larger and come in huge carrying cases.

How do they compare for the size of items you can test?

The M24 has a tiny 'well' (indentation) which you fill with acid, you must 'dip' the item into this, that limits you to testing very small items. The Gemoro (AGT) testers have a good-size test plate which will take all but the largest items of jewellery. The Kee has a smaller test plate (large enough to test most jewellery) and also comes with a second set of connecting leads for testing items that don't fit onto the test plate.

XRF testers (also known as "x-ray guns") cost between £12,000.00 for a 'basic' handheld model, to £50,000.00 for a good quality desk model. They display a chemical breakdown of the metal, listing not only the percentage of gold but also the percentage of all the other metals. An example: an XRF tester might tell you that the metal contains 44.3% gold, 14.03% silver, 0.6% platinum and 0.05% Palladium. Our electronic testers will tell you it's about 9ct (37.5% gold). We do not sell XRF testers.

How do they compare for speed of testing?

AGT1: slightly faster than acids.

AGT3: when set to enhanced mode is about the same speed as acids, though there's not a lot in it, and it depends on the carat. The quick mode is much faster than acids but isn't accurate.

KEE: faster than acids.

XRF: has quick and enhanced modes. On enhanced, it is slower than both AGTs and acids (the videos always show them in quick mode!)

How do they compare for safety?

AGT, KEE, ANALYZER and PRO testers use a probe containing a harmless salt solution, the M24 tester uses acid.

XRF testers use x-rays, when used properly they present no risk. However, we see them used by dealers who hold items in their hands whilst testing, and so give themselves a dose of radiation several times per day. There is a high chance that this will give them cancer. Needless to say, they should never be pointed at a customer!

Acids must be handled with care. Providing it isn't spilt on skin (simple solution: wear gloves) the level of exposure becomes nil.

How do they compare for consumables? (prices include VAT)

AGT pen-probes and Kee pen-probe cost about £50.00. They are like felt pens, they contain a harmless salt solution. Both manufacturers say they last "up to" a few thousand tests. AGT pen-probes are not guaranteed, that means if it stops working after a few weeks (or a few days) you must buy a new one. Kee pen-probes are guaranteed for one month. A survey of our customers indicates that KEE pen-probes last between 3 and 18 months (anywhere from a few dozen to few thousand tests). If you can get them to last several months, it's good value; if you find they only last a few weeks then it works out expensive. We don't know why there is such a variation, our best guess is that customers don't replace the caps firmly enough and they dry out. ANALYZER and Auracle PRO pen-probes, we haven't yet sold enough to get feedback but teh suppliers say they last longer than the others. M24 bottle of contact fluid lasts about 50 tests and works out very expensive.

A Bottle of acid costs about £15.00 and lasts for 100 to 150 tests, very good value.

An analogy would be that of ink cartridges. A pen-probe is like an all-colours-in-1 cartridge, once the cartridge is 'used up' you can't print (like a pen-probe being used up) - as opposed to a cartridge for each colour (like an acid for each group of carats) where you can just replace the one that is used up. For a busy shop this could be the difference between spending £50.00 per month or £15.00 per month on gold-testing.

XRF is different. When an XRF tube wears out, a new one will cost from £2000.00. Plus a service, plus any repairs that are needed, plus VAT...assume £3000.00.

How do they compare for service and repairs?

KEE TESTERS. We give a one year guarantee. During that year (and providing we are certain that there is a fault) we will replace it. The suppliers do not offer a repair service, though we can carry out basic checks (battery, connecting leads, calibration) and we also know how to reprogram the microchip.

We find that GEMORO (AGT1 and AGT3 TESTERS) will replace any that are faulty in the first 14 days IF they are returned in absolutely 'new' condition but not if there are any signs of use. Their guarantee is very strictly six months. Any returns to the USA take 2 to 3 months, They do not offer a repair service, if your Gemmoro breaks down one day after six months, you are expected to throw it away and buy a new one (in the US this is expected of low-value items that cost only a few hundred pounds).

The M24. It's very simple - not worth repairing. Also be aware that the contact fluid is a strong acid, you must clean the 'well' thoroughly after every test, otherwise the acid dissolves it.

A CHEMICAL TESTER cannot 'break down', you simply buy a new bottle of acid.

Which tester is the 'least destructive'?

Every tester (whether you spend £15.00 or £12,000.00) only tests the surface. This means you must file the surface with a fine needle-file (supplied with each tester) in a place where it won't show, to remove any surface plating. There are no exceptions. If you are not prepared to file surface then you cannot test jewellery with an electronic or acid tester, you cannot buy scrap, you cannot test anything, you cannot deal in precious metals.

Acid (including the contact fluid of the M24) leaves a stain, this can be polished off. The AGT and KEE testers can leave a very faint circle of salt which wipes off easily, or a very slight stain if you repeatedly test the same spot (it too can be polished off). The only time this is ever a problem is with brand new items polished to a mirror-finish, unless you are a professional polisher you won't be able to restore the mirror-finish. XRF leaves no mark (though you still have to file the item).

How do they compare for testing silver, platinum and Palladium?

Mizer and AGT testers can only test for gold. KEE testers can also test for platinum (with care). Acids can also test for silver, steel, platinum and Palladium. XRF can test for several more metals including copper, tin and zinc.

How do they compare for calibration?

Every gold tester has to calibrated. Calibration is the matching of the electronics to an actual sample.

If you haven't used a bottle of acid for some time (they get weaker over the weeks and months) you must check it against known samples (e.g. any item with a UK hallmark).

The AGT testers need to be checked against a 14ct sample, you press some buttons, the electronics calibrate the machine to the sample. You will need to do this whenever you turn the machine on. This is frustrating when you are testing dozens of items for a customer and it keeps telling you to calibrate. Sometimes the calibration procedure fails and you have to do it again...and again...and maybe a fourth or fifth time.

The KEE tester must be calibrated against a sample of 18ct, you test the item whilst turning a knob until it reads exactly 18ct (and to test 20ct to 24ct accurately you must also calibrate it against a 22ct sample too) - turning a knob is very simple. You do not have to do this every time but it's a good idea to do it more often as the fluid in the pen-probe gets low.

The M24 tester cannot be calibrated, you just have to hope the readings are more or less correct and don't 'drift' over time.

An XRF tester must be sent back to the supplier if it needs calibrating. If that's all that is required, it will only cost a few hundred pounds, but a repair can easily cost £2000.00 or £3000.00.