So (if I'm understanding) basically we
tend to use BTC - but the financial industry is suggesting something like XBT to be more in line with supranational designations:
https://en.wikipedia.org/wiki/ISO_4217In addition to codes for most active national currencies ISO 4217 provides codes for "supranational" currencies, procedural purposes, and several things which are "similar to" currencies:
Codes for the precious metals gold (XAU), silver (XAG), palladium (XPD), and platinum (XPT) are formed by prefixing the element's chemical symbol with the letter "X". These "currency units" are denominated as one troy ounce of the specified metal as opposed to "USD 1" or "EUR 1".