Hello all,

I received my TM-8811 ultrasound device, 129 euros, from Hongkong, took about 11 days to get to me after internet order (eBay).

I tested a Johnson Matthey 100 gram silver bar and a ICC 50 gram gold bar and an american gold eagle. Both were above the minimum thickness measured value of 1.2mm.

They all worked ok, taking into account that the accuracy of this device is +-5%.

So, if you look into the sound velocity tables, silver would overlap with tin and platinum.

So, this measuring method is not 100% good, first you need to know the dimensions of your test sample, then weight it, and hence calculate density. After that is done, you can rule out tungsten (for gold) or molibdenum (for silver) by checking the speed of sound in the material.

Bottom line: you need both methods of assaying (density and speed of sound), then it is fool proof. In my case, I think both methods are necessary if you buy bars (1 oz and above). For smaller coins the accuracy of the tester is not enough, IMO.