It was Bill Clinton that pioneered tungsten cores. The theory is that he and his gang plundered US gold reserves and covered up the crime with gold foil-wrapped tungsten bars. Some were later shipped to the Chinese, who discovered the fraud. Hence all gold entering China must now be melted down and recast. There are definitely fake gold coins coming out of China, and these are being sold on eBay - usually as fake coins, but there is nothing to stop them being sold as the real thing.

https://www.thelibertybeacon.com/clintons-federal-reserve-stole-fort-knox-gold-wake-up/