About that: note that in the ISO standard for those 3 letter currency codes, the first two letters represent the country or union that issues the currency. For instance, there will not be another GB* currency that is not british. And BT* correspond to Bhutan, IIRC. So BTC is problematic.
The ISO 4217 currency codes [1] look pretty arbitrary too. For example, why is the Afghan afghani "AFN" instead of "AFA", or the Japanese yen "JPY" instead of "JAY"?
It's JPY because the ISO 3166-1 alpha-2 2-letter country code for Japan is JP. Similarly, it is GBP because the ISO 3166-1 alpha-2 2-letter country code for the United Kingdom is GB, not UK. ISO 3166-1 alpha-2 is used everywhere, for example on the web for ccTLDs (although the UK is an exception, since it has GB allocated, but for backwards-compatibility with another network, it also got UK, and now disallows registrations on GB).
Yeah, which is kind of weird when a country revalues their currency. For instance, Mexican Peso was the obvious MXP, then it was revalued so they needed something new, so it's MXN (Mexican Nuevo Peso, I guess). Similarly, Turkish Lyra went from TRL to TRY ("Y" for "Yeni" meaning New.)
So then Bitcoin should adopt ‘EAB’ (Earth Bitcoin)? Or ‘WOB’ (World Bitcoin)? That'd be fun, a Bitcoin penny could be called an Erby or Wobby (that's about USD 0.90 right now).
For practical reasons, the ISO 3166/MA has "reserved the two-letter combination EU for the purpose of identifying the European Union within the framework of ISO 3166-1".
