It's entirely possible Grace might go through a canon last name change in the future, because seriously, even I can't remember how to pronounce Sciuridae half the time.
Not that I'm super good at pronouncing thing. It's just I'm the one who chose that name.
I had considered poking fun at post-apocalyptic currency in the Fallout games. In those game, pre-apocalyptic bottle caps are used as currency. This is initially for pretty reasonable lore reasons having to do with them being finite, nigh-impossible to duplicate, and being backed by purified water (much like how our paper money was once backed by gold).
Now it's more like "it's Fallout, so money has to be caps even if we make a game before caps were established as currency".
ANYWAY, given that gold coins are the currency in most fantasy games, and (I think) those would be just as fine as bottle caps after world ending dragons exploding, I decided not to bother with any sort of invented currency.
Besides, it would have to be something sillier than bottle caps, and bottle caps are already pretty silly.