methods for backing financial transactions

[Klpno]

Hi, everyone.
Once again I'd like to ask a question about somewhat unclear phrase from the book written by a british historian. What does the phrase 'methods for backing financial transactions' mean? I think that 'methods for backing financial transactions' are means of payment used in financial transactions but I'm not sure.
As in the past, the international economy depended on a number of key mechanisms. It needed a recognized monetary unit for transactions - in the past this was normally gold and silver coins, hence the importance for western Europe of its control over the resources of the Americas which enabled trade with Asia to be financed. For much of the twentieth century this remained the case, although individual currencies, at first sterling and then the dollar, played a central role. Eventually, just as in individual economies paper money had replaced coins as assets (something pioneered by China around 1000 CE), so in the international economy intangible assets and entirely artificial units (such as 'Special Drawing Rights') replaced gold and holdings of foreign currency as methods for backing financial transactions.

[Mister Micawber]

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'Backing for financial transactions' here means anything accepted as of intrinsic value-- gold, silver, assets, SDRs-- which can be used to guarantee debts.
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Native English teacher at Mister Micawber's

[Klpno]

Thank you very much again, Mister Micawber!!!