Secondary Currency

[Nanoha Takamachi]

"All Omnilium owned by Primes is part of their being, and cannot be given or stolen - only used. Secondaries, on the other hand, cannot store Omnilium within themselves, and must transport it physically. Secondaries also cannot use Omnilium to summon, but they can 'extract' it (see below), separate it, and combine it (which is simply a physical process of pulling it apart and pushing it together). It is the main source of currency in the Omniverse."

So yeah I guess Omnilium is used be secondaries, but I assume it is probably converted into a physical form of currency for them to use (consider it like gold, then turned into coins). I've sort of pictured a credits system in Coruscant where people use a digital form of currency that is a representation of the omnilium stored away somewhere in banks or whatever. Perhaps Camelot would use actual gold coins or something.

Greg might have an actual 'canon' representation in mind, but he might've also left that detail vague on purpose for us to develop ourselves.