@petrv Sol rolled back to Solar :-)
It's not that difficult to set-up an internal currency: just to take a name (let's we say "asgard", XAS, for simplicity?) and let's say "you make the (useful) software application ABC, place it into Asgardia's MarketPlace (MP from now forward) and other asgardians can buy it for 100 XAS".
First problem here: if no one have any XAS into his (digital) wallet, how can anyone buy from MP?
Solution: let's say "each (certified) asgardian will receive 10.000 XAS into his/her own digital wallet, to start the internal economy"... how much is "10.000 XAS"? much? few? enough? it depends on the "(market) value" of the goods, so on the "exchange" we can think the XAS can have with other currencies on which our actual "value system" is based.
Let's say 1 € = 1.000 XAS, we can see we received 10 € "value" (or 10,72 $ at now), which seems "a few".
This is only a start, to place a base of reasoning: as we're thinking about an exchange (or "exchange rate") from XAS to €/$/whatever we're comparing "numbers" not "the value". Steps may be taken to officialize our internal currency and to create an exchange rate system in the exact way the SecondLife's Linden Dollar (L$) have an exchange rate with USD (and, thus, with all the other values 're having exchange rate with USD too), and SecondLife is not a Nation (it's a virtual world based into USA).
A step forward can be the one intended to "convert" (AKA buy/sell) international currencies into XAS, so that asgardians (but not only) can buy (or sell) goods via MP. This can also lead to make profit, by selling via MP (remembering there must be applied international taxes, e.g. VAT, to the transactions that must be taxed into the buyer's country). E.g. I can "invest" 100€, buying 100.000 XAS, so to have something in my wallet to (a) buy goods from MP, (b) pay Asgardia's taxes, (c) exchange XAS with asgardians' goods directly even, not via MP, etc.
So, we can see, to create an internal currency system and to relate it to external markets via the exchange rate is not that big burden.
All the transactions that will take place into "asgardian economic sphere" will happen electronically for sure (so that we won't need to coin physical money), so even international regulations on anti-money-laundering will be respected as transactions will be fully traceable even out of MP.
All the XAS an asgardian will earn will be directly expendable, if to pay something to another asgardian, MP or asgardian's taxes or services, or indirectly (after exchange) to pay other countries' goods. Let's say I have 100.000 XAS I can pay something which costs 100€ into EU (or 107,2$) by converting XAS/EUR (via PayPal for example).
The Asgardian Stock Exchange, allowing to buy or sell XAS into other currencies, will establish the "actual exchange ratio" exactly like other currencies' does.