Since the story about the fake gold tungsten bars surfaced awhile back, I have been skeptical. I see that Lou has similar feelings about this and I agree with all he said.
The highest density I've found on the internet, for anything fabricated from any form of tungsten, is 18.75. The difference between this and the 19.3 of gold is not that great, when it comes to measuring the density. If the bar weighed 400 oz (12,440 grams - 27.4#), the difference in the weight in water, between densities of 18.75 and 19.3, would only be .6 oz - about 18 grams. However, Sartorious, Mettler, and other companies make scales that will weigh 35 kg and have a readability of .1 grams. So, with a little jury-rigging, these could easily be used to determine the density.
The thing that bothers me the most is the appearance. The only thing that looks like a cast gold bar is a cast gold bar, with it's ripples, depressions, minor blemishes, etc. No other metal I've ever seen, when cast into a bar, has the surface appearance of a cast gold bar. Even if tungsten could be cast, the surface would surely look nothing like gold. If the surface were machined, it wouldn't resemble a cast gold bar at all.
Another problem is that the color and the variation of shine of a cast bar is different than that of a gold plated bar - just compare the color and appearance of a pure gold bead with a gold plated article. The best way to see color differences on shiny objects is to cover them with Kleenex and then wet the Kleenex with a few drops of water.
Anyone that has worked around pure gold bars would surely be able to tell the difference, visually. I can see no possibility that the appearance could be duplicated with a gold plated tungsten bar. I don't doubt that the gold plated tungsten bars existed. However, whoever accepted them was stupid or inexperienced or both. They also could have been involved in the scam.
I agree with Lou about the difficulty of plating on tungsten. If you look on the internet, you'll find cycles for it. All that I found, however, required a chrome strike first, followed by - nickel strike, nickel plate, gold plate. I would think the nickel would be attracted by a strong magnet. I found none for gold applied directly to the tungsten. Plating on molybdenum is as difficult as plating on tungsten, for the same reasons. Many years ago, I refined a drum or two of moly disks, about 2" in diameter, that were heavily gold plated. They came out of some type of rectifier, where they were arranged in stacks.
Chris
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