The store of value being the metal itself for a long time: at first silver, then both silver and gold. Metals were mined, weighed, and stamped into coins. This was to assure the individual taking the coin that he was getting a certain known weight of precious metal. Coins could be counterfeited, but they also created a new unit of account, which helped lead to banking.

The ratio of investment to actual value is called “leverage”. Using a $1,000 to buy a Forex contract with a $100,000 value is “leveraging” at a 1:100 ratio.

It is important to remember that there are other ways of financing a deficit: borrowing from foreign banks or attracting net FDI inflows. But since FDI flows have been negative and bank flows tend to be small, most of the financing the US needs has come from the sale of longterm securities to foreigners.