Well, the value of money in those days was not fiduciary but intrinsic. It was about solid coins, and those favoured were made of silver and gold, not minding their numeric value but instead their weight; in that, real business was made with coins of known reputation. One of the most reliable was the silver thaler, which lasted for 400 years (the dollar descends from it). Gold coins were also reputed by their metal purity. On the other hand, and going back in time, Roman coinage could be good for internal use, but it is known that, at least silver denariums were either underweighted or of low purity to cope with momentum inflation.
But i realize taverneers and traders, altough illiterate, knew a whole lot about this ... much more than me, i am sure
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