Fraud in gold sales: Yup. china is where all the fake gold bars and coins come from. One of our local coin dealers got burned for 40,000$ when he bought a handful of supposed gold ingots. Good looking pieces. Nice numbers and proofs. Even passed the wipe test. But they were gold over lead. The only give-away was the bar thickness which the dealer forgot to check. These things had been sold for, as I recall, about 40 bucks apiece. But the dealer bought them at spot which had been about 2,500$ at the time.
Sheesh, there was S. African made device that would easily detect fraudulent coins on size/weight for sale a few years back.
Dealing with bars I’m surprised that the dealer didn’t check the specific gravity with a calibrated beaker and a scale.
You can probably fabricate pretty close to foolproof fakes with a little time and effort by use of tungsten (slightly higher specific gravity) of volume X milled down to a level that will allow for a dipping or heavy plating of gold that ends up reflecting the gold specific gravity for the given volume. Large bars of gold get drilled to defeat this, and I’d be willing to bet that unless the plating/coating is of sufficient thickness to dampen it, the “ring” (tone) of the Tungsten bars will be substantially different.