"This is a Silver Sikka, from Prayad. Note the distinct cutouts on the side of the coin. Over here is a gold Kolik tradebar, from Kylmaken, with their symbolic Hydra embossed on it. And this one is a simple copper Brenye from Delbiro - it isn't worth much, but the scythe on the tails side is rather interesting."
Now fantasy numismatists can learn the varied side of economics - and your scifi heroes can carry pocket change, as well!