Verification Of Poured Gold Ingots-Most Accurate Methods

My local coin store has a professional large XRF analyzer. For hourly fee they test coins/bars for metal content and will provide a letter of the results and appraisal. Most portable XRF analyzers coin collectors use are small and good for coins, but they are not powerful enough to go deep into a large bar to see if it's gold all the way through. The family could try to find a coin dealer in the area, ask if their XRF can test large bars. Just a surface chemical test is not enough. They may need to contact a refiner or gold mining company.

If genuine, family needs to protect these. Options are bank safety boxes, good quality home safe, etc. Some insurance companies insure high dollar valuables as an addition to home owners policy. They usually want an appraisal or some other documentation of value. I think they charge so much per month for each thousand of coverage.

If family keeps these bars at home, advise them to NOT tell anybody. Keep it quiet. News reports of coin collections being stolen at home are often the result of someone learning about the collection being there.

If family wants to sell, they need to get several offers from several dealers, local coin stores, the major online dealers. My local jewelry store buys gold bars, jewelry, but I don't know if they are good offers. I would not sell at a pawn shop.

Without re-smelting the bars and taking out other impurities or metals, it is hard to know the true percentage of gold content. You can contact metal, mineral or gold assay companies, mining companies, and talk with them for more information. The bars could be gold plated as they were poured, but inside could hold for instance lead, iron, etc. Good luck in your findings.

real gold would be worth $2.5 million
Would the deceased be in a position to own that much?

XRF only tests the surface of the bar.
Tungsten has a density very close to that of gold.
A fake gold bar with a tungsten core will test genuine for weight and XRF.

Fake counterfeit Credit Swisse and Perth Mint bars with a tungsten core have been discovered, which easily pass any XRF test and also test very accurately for weight.

They were discovered by placing a suspect bar on a very sensitive scales and holding a very strong magnet about 1mm over the surface of the bar and measure for a very slight decrease in measured weight.

Hand held XRF instruments still unable to test for very high purity of gold; they are only good for about +/- 0.2% accuracy.
They are no good to test for less than 0.1% impurities.
They are, however, perfectly OK for testing deliberately alloyed jewelry gold, such as 9ct, 14ct, 22ct and .900 coin gold.

Yes an XRF only goes a little below the surface but would be a good first step in analyzing the bars. Here's an old YouTube video of someone using ultrasound waves to test through a large gold bar.