'This time is different' however, as overnight reports via Australia's ABC News claims that the historic Perth Mint is facing a potential $9 billion recall of gold bars after selling diluted or "doped" bullion to China and then covering it up, according to a leaked internal report.

Gold doping is a somewhat accepted practice in the industry and is not illegal, but is high risk for refiners, as it lowers the quality of bullion by adding impurities like silver or copper.

[ABC News] uncovered documents charting the WA government-owned mint's decision to begin "doping" its gold in 2018, and then how it withheld evidence from its largest client in an effort to protect its reputation.

While the gold remained above broader industry standards, the report estimated up to 100 tonnes of gold sent to Shanghai Gold Exchange (SGE) potentially did not comply with Shanghai's strict purity standards for silver content.

One Perth Mint insider, who asked not to be named as they could face five years' jail if their identity is revealed, says it is a "scandal of the highest level".

"I don't know if I've ever seen one this big," they say.

The mint began doping its gold as a cost-saving measure in 2018, expecting to save up to $620,000 a year - a tiny fraction of its annual sales.

"At all times the gold bars the Perth Mint produced and sold contained at least 99.99 per cent gold, as per their specifications. This has never been in dispute," the mint claimed in a statement after the news broke.

"These purity specifications are aligned with industry standards and akin with those set by the international market authority, the London Bullion Market Association.

"In September 2021, the Perth Mint was made aware that some of its one-kilogram bars may not have met the non-gold specifications of the Shanghai Gold Exchange (SGE). The SGE specifications demand that the non-gold component – that is, 0.01 per cent of the bar or 100 parts per million (ppm) – contains no more than 50 ppm silver."