[null and void]

Think you gotta drill sample it.

Worse comes to worse, yes. But if there is a nondestructive method that would be preferable.

X-ray, neutron activation, ultrasound, mechanical deformation (does the bar bend, twist, flex or stretch like solid gold?), sonority, center of gravity, something.

[bert]

The tried and true test is to bite it. If there are teeth impressions, it is likely gold. To test purity, use a touchstone.