When your MBS or junk bonds are no longer accepted as collateral you have to dig deep into the vault and come up with something that is accepted, like gold or silver.

FORBES: Gold Inches Up As Goldbugs Seek Reasons For Historic Rout

Unlike diamonds and gold, there is no widely-accepted price list that sets sapphire values, which makes for tricky investment planning.

FORBES: Kate Middleton Engagement Ring Spurs Sapphire Sales

We started that century with a fundamental international currency, gold, which kept its value through time and was widely accepted around the world.

WSJ: Manuel Hinds: The Case Against Floating Currencies

While the Presidential Advisory Commission accepted that the US was responsible for the goods on the Gold Train, it did not suggest how property could be returned or compensation made.

BBC: US in dock over Nazi loot