The analogy is obviously a reference to times past when gold and silver coins were used as money but the using the analogy for different cryptocurrencies is nonsensical. The reason they used different metals of different values was simply to have the ability to make change. Gold coins worked great for settling large debts across oceans. Silver coins worked great for such things as paying wages. But someone going to a grocery store with gold coins was even more problematic than someone going into a convenience store with large bills. The need for making change was even present with the silver coins so they broke dollars into half dollar, quarter and deci (dimes) coins. Even more change making ability was garnered with the nickel and the penny. The PROBLEM with having different metals was that the relative values between them would vary by supply and demand. Who, for example, determined once and for ever that 100 copper coins of a certain weight was worth one silver coin of a certain weight? That practice was basically a case of government price fixing of the prices of silver and copper. A crypto currency is divisible to so many decimal places it never needs any other “coin” in order to make change. Crypto eliminated that need and a transaction returns the “change’ back using the very same crypto.