If I owned a Celestial coin, I would file it under "C" in my world coin collection. I would not, however, consider it a "real country" and therefore not include it in my list as published on the thread january1may linked to.
To qualify as a "real country" in my mind, I require at least two of the following three criteria to be unambiguously met:
1 - a formal claim of independence or existence with respect to a specific defined territory, preferably recognized by at least some other recognized countries;
2 - a significant "native" population within the claimed territory who recognize the claim of independence or existence, either formally or de-facto (eg by paying taxes or receiving government services);
3 - a demonstration of continuous and unchallenged control over the claimed territory.
The Confederate States met all three criteria, therefore qualified as a "country" for the period of its existence.
Transnistria and Somaliland meet all three criteria, therefore likewise qualify.
Islamic State meets all three criteria, though #3 is currently in doubt and the extent of the "claimed territory" is also somewhat dubious, but if they were to get around to making coins, they likewise would qualify. Not that I would want to buy one.
Taiwan fails #1 by refusing to declare independence (though it nevertheless has some international recognition) but meets #2 and #3, so likewise qualifies.
South Georgia and South Sandwich Islands fails #2, having zero permanent population, but meets #1 and #3, so therefore qualifies.
Hutt River and Sealand meet #1, don't quite pass #2 (essentially lacking a "local" population) and are ambiguous on #3 (as the legitimate owning government simply hasn't tried reasserting control to any great extent). In my judgement they do not qualify.
Celestia met #1 (barely; no other nation recognizes it). However, it radically failed both #2 (it had zero "native" population) and #3 (it singularly failed to prevent incursions by military and civilian units from other countries into it's "territory" and failed to prevent the ratification by all spacefaring nations of the Outer Space Treaty of 1967 which declared Celestia's "territory" to be unclaimable). Therefore it was clearly not a "real country".
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis