a variety of gold alloys are imo best used in ways that narratively suggest and lead to extinct cultures and technology, ideally with strange markings and found with cultural artifacts that send the party to a sage who can direct the party as to their significance in a manner that furthers the campaign. (Alternatively a high-level bard might just make a lore roll, or be told by the DM to smooth gameplay.) Electrum has been a part of standard D&D rules since at least 1st ed. one coin generally worth 1/2 a gp.

https://en.m.wikipedia.org/wiki/Electrum

Naturally occuring gold/silver alloy. Used for the earliest known coins, the caps of Egyptian pyramids, etc.

Money is money.

I mean for rarity value alone they gotta be worth 2, 3 gold each

“Oh shit, is this the Mistborn universe?”

Not usually, but as parts of unusual treasure, yes. But I've always been prone to building treasure as part of the story, in a group where the story is the main style. Doing hack/slash or a roleplay heavy dungeon crawl, I just go with standard treasure for the encounters though.

The dragon had OCD and couldn't stand seeing coins everywhere piled up. So they traded it all in for electrum and stored it in an extremely rare relic known as a Sāflok.

https://www.youtube.com/shorts/pTl5oIgOGXk

In my setting, I just use them like a $50 bill.

I like to use them as part of treasure hoards for creatures that are either primitive or ancient, as a nod to the difficulty in separating the alloy. For the latter, sometimes the coins have value as archaeologic artifacts moderately higher than their own value, if the party invests their time and ration resources to find someone to pay that much.

What’s an electrum

I played with a DM who only used them in elvish cities, no one else would trade in them. That is now in my world too.

Smug elves and their special currency.