[Toddsterpatriot]

You can test the purity of gold yourself with the right test equipment. Mostly this consists of acids which you can purchase for that purpose

Are you going to dissolve the entire bar?

[expat_panama]

You can test the purity of gold yourself ...

What's so hard about measuring density?  A typical high school chem lab balance can tell us purity to one part in a thousand for the whole bar, and it's non-destructive.

[Travis McGee]

To test 400 oz gold bars, one assumes the tester will have enough sophistication to be able to determine the vast thermal, stiffness, hardness and electrical property differences between gold (very soft) and tungsten (very hard).

And if there is any question, a 1/8” simple drill bit will solve the conundrum in a few seconds.