Diamond Selector II testers - genuine or fake?


We had a few hundred of the original Japanese Diamond Selector CULTI diamond tester, they sold out in August 2023. There aren't any more anywhere in the world, all the Diamond Selectors you see are Chinese copies. 

Although the original Japanese version was the best, not all Chinese copies are 'bad'. All Diamond Selectors look the same on the outside but the quality of the components varies hugely. This affects the reliability, both in terms of giving correct readings and in terms of breaking down completely.  

In the chart below, the more features you can see that are listed on the right, the more likely it is to be a copy.

Original CULTI Diamond Selector II, made in Japan Copies of Diamond Selector II, made in China

The instructions are on glossy paper in reasonably good English, and the guarantee slip is in English too.

Some of the copies have the same paperwork as the original, but many instructions are written in poor English; sometimes the guarantee slip is in English and Chinese (definitely not the original Japanese model!)

If it has no instructions at all, be suspicious. If the instructions don't seem to tally with what you have in front of you, be suspicious. If there's no guarantee slip, be suspicious.

The cardboard box: in addition to DIAMOND SELECTOR II it has the CULTI logo on four sides, and Made in Japan culti on two sides.

The box is just marked DIAMOND SELECTOR II, and nothing else.

The pouch is embossed CULTI on the flap.

The pouch is unmarked.

The pouch is made of a good quality vinyl and has an open compartment (containing the stone-holder) on the outside at the bottom.

The pouches vary a lot on the copies, some are thin vinyl, on some the stone-holder compartment is fastened with Velcro flap.

The chart on the back of the tester is marked in degrees Celsius.

 The chart on the back of the tester is marked in degrees Fahrenheit.  

Under the chart on the back of the tester is Made in Japan culti.


The sensitivity knob (marked, "volume") works smoothly.

The sensitivity knob (marked, "volume") might work smoothly, but is often too stiff or too loose.

The battery wire is three inches long, easy to replace battery.

The battery wire is only two inches long, fiddly to replace battery, the wire is easily broken, this is not covered by the guarantee.

The segments of the LEDs go like this: 4 green then 4 yellow then 4 red.

There are variations from manufacturer to manufacturer but, typically, 4 red then 5 orangey-yellow then 3 blue.



DIAMOND SELECTOR II (Chinese copy), OUR REF. DT-DS. Chinese copy, good quality. I know this particular factory well, they are not the cheapest but they only use good quality components and are reasonably good with their quality control. These testers only work at room temperature (between 18 degrees C. and 27 degrees C).  Within this temperature range these do give a correct reading most of the time (correct maybe 80% to 85% of time, I guess).  

(This item sold out in 2023)
Although these are more expensive than the copies, we are selling them for a fraction of the original retail price, this is good value for a 'cheapie' that works well.  As with the others, they must be used between 18 degrees and 27 degrees C. to give correct results.  My best estimate: they give correct results 95% of the time.


The most 'basic' quality, just like you see on eBay and Amazon. They do look identical to the other Chinese copies but their components are cheap and the reliability poor. I did once sell these, but most were returned within a few months because the readings were inconsistent or they simply fell apart.  You can find these for under £20.00, this is the one to buy (not from us!) if you want the cheapest but don't care if it works. My best estimate: they give correct results 70% to 80% of the time.  


All of the above are diamond-only testers, they will distinguish diamond from most other stones but not for the manmade stone Moissanite - all Moissanites will show up as diamond on all the testers listed above. For combined diamond/Moissanite testers see our various 'multi tester' models.