Right, but the issuing country (and whoever the ruler was at the time the coin was minted) are required information for determining the metal content, unless you literally destroy the coin.... so coins from certain issuing countries with certain rulers on their heads could be accepted as more valuable than others if you could find someone to trade with that also had that knowledge.

There was another interesting article that I read yesterday about a late Roman hoard that was found in Spain that had coins minted by several Emperors after Diocletian's reforms, with a vast majority of the coins being minted by Diocletian.. on that one, the researchers hypothesized that the hoard was literally representative of a payment during a Venezuela-like inflation crisis and that the Diocletian coins were valued higher because they were known to have the highest silver content.

That isn't to say there weren't preferred coins though. If a coin wasn't common enough to be recognized as silver other commoners or even some merchants might not accept it out of caution.

This is partially why the roman Denarius is found everywhere. Not only were a large amount minted but because the empire sprawled so far and wide it was easily recognized as silver. The romans even had to set the value slightly above the value of the metal content to help encourage people to keep the currency within their borders.

Oh I didn't know this! Thanks for letting me know.