I've never really understood what makes pretty printed paper and alloy minted coins valuable...or for that matter, what makes precious metals so precious...it's not like there is a limited quantity of any of this material...
Trees are grown daily to make paper...inks are made from several different chemical concoctions so there's no shortage of supply there...and if metals were so damn precious, we would've strip mined all the raw material by now...hell, we've been enamored with gold for millennia...and all because it's a shiny soft metal...
All that being said...there are coins in circulation right now that can bring more than face value from the collector's segment of the market...so many in fact that it might not be a bad idea to take a look at that jar of pennies, dimes, and nickels over there in the corner...