It varied. Some countries used a bimetallic standard with fixed exchange rates, some used one as the standard and let the other float. There's even been trimetallic(gold/silver/copper) at times.

It's actually been a political issue which of those to use more recently than you'd expect(and no, I don't mean Ron Paul) - the 1896 US Presidential election was fought in significant part on a Democrat plan to move to a bimetallic standard away from straight gold, which was in the day an inflationary move designed to help indebted farmers. If you've ever heard of the "Cross of Gold" speech by William Jennings Bryan, that was it. A couple decades earlier, though, the US was bimetallic, and routinely had one metal or the other sucked completely out of circulation by prices changing faster than the official exchange ratio, as is to be expected of a system with fixed exchange rates and no capital controls.

The history of how to abuse commodity money systems(both from the public's perspective and from the minter's) is long and actually rather fascinating. If you ever hear someone talking about how gold is stable and can't be abused, you can feel free to laugh at them.