-Papa! what's money?
-What is money, Paul? Money?
-Yes, what is money?
-Gold, and silver, and copper. Guineas, shillings, half-pence. You know what they are?
-Oh yes, I know what they are. I don't mean that, Papa. I mean what's money after all?
Little Paul Dombey, Dombey and Son, by Charles Dickens (1848)

sovereign bonds

...or, the six short years when markets lent Greece as cheaply as Germany