genesis of gold-tungsten: the rest of story, page-2

The 1090 Flaw Detector allows you to look into gold bar for voids/defects as well as UT velocity which is determined the products elastic modulus i.e Tungsten Velocity is 5183-5460m/sec and Gold is 3,240m/sec. For example if you calibrate for Au then the testing Tungsten bar of the same thickness, the UT thickness would read approximately half the actual because of the speeding-up of the sound through the Tungsten.

No professional institution would accept a gold bar as such without this test.