As a matter of definition, yes. I think that a free market would probably have a “standard” of varying rates of exchange between precious and base metals, with all of them seeing use as money in certain circles. Decametallism with gold, platinum, palladium, silver, copper, nickel, chromium, iridium, molybdnum, and tantalum.
Wouldn’t the market decide this? There is alot of talk about the gold standard but if competing currencies were allowed I could easily imagine other currencies that I would accept especially from companies who proved themselves to be trustworthy and transparent. Big box stores could create their own currencies redeemable for their goods and pay employees and suppliers with them, possibly at a rebate, if both parties so chose. Digital currency exchanges where these were traded for commodities, such as precious metals, could be setup easy enough to work on the fly with mobile telecommunications. If there was complete freedom in monetary issues I think it would be very hard to say exactly what would be innovated today.