“When the Brits got some of theirs back, it had been re-cast. A chemical analysis showed that the bars had been diluted with base metals between the date we got it and the date we gave it back.”
Do you have any source for this? I know some have recently found bullion on the open market that was debased with tungsten, but I had not heard that any of it was sourced from the U.S. government.
Apparently, the bad guys acquire real gold bars with appropriate official markings. Then they drill out most of the gold and replace it with tungsten, which has almost the same density as gold. However, the speed of sound in tungsten is quite different from that in gold, so it is easy to detect fakes non-invasively with an ultrasound scanner (video).
Glenn Beck had the references on his radio/cable show. I don’t remember them as I sit here this morning.