what are these things called "coins" that you speak of?
They're the archaic precursor to debit cards. Similarly thin (well, a bit thicker), made of metal instead of plastic, and - get this - round (about 1" wide). They were one-time-use microtransaction tokens, completely anonymized
without cryptographic tagging, so cheap and common that rather than swiping the thing you'd just
give it to the seller. Sucked for online purchases though: you'd have to take a big heavy pile of them (made of metal, remember, and contained fixed microtransaction values) to a brick-and-mortar (marble-and-steel actually) storefront service which would convert them into transaction tickets on processed dead tree carcasses (data expressed in plaintext even! really! security practices were hideously lax), then have to pay someone to
carry the token to the recipient (lag times were atrocious, I mean like
days), where they'd reverse the process.
Somehow, use of "coins" correlated with a fad involving small printed portraits of dead presidents (the most desirable being a portrait of some guy most people
thought was president but wasn't). Pretty lousy portraits too, high resolution, but color depth was pretty much limited to green, black, and a crummy off-white. And - get this - you'd get thrown into a small metal box if you so much as tried to get a printer for making your own (friggin' expensive printers too). Pretty popular fad; everyone was obsessed with collecting them, even though there were only about a half-dozen portraits involved, everyone wanted thousands of 'em, even
millions.
20th Century was weird. Let's not go back there.