> Countries don't all use their own currencies

Sure. I think this missed the point.

I didn't say/intend "a country / army needs to be backed by a unique currency"

I said, "For a token to be a currency, it needs to be backed by [at least one] army and [at least one country's] taxes".

e.g. The Euro happens to be backed by multi armies and at least Germany's taxes.

> Some countries don't have any armed forces unless you count the police.

Again, it isn't "their army" but it is "an army". e.g. Liechtenstein is backed by "Austria and Switzerland under an informal agreement among the three countries." https://en.wikipedia.org/wiki/List_of_countries_without_arme...

Anyways, if we disagree that is ok too. All of this is quite fuzzy really.