I can not promote someone to the same rank as me, nor can I promote myself to a higher rank.
It is organizations that set the rules of who can promote to what dan. Many orgs, and if I'm not mistaken, the Kukkiwon until recently, only allow you to promote to two grades below your own (4th can promote up to second, 5th up to third, etc.). But if your school is independent, then realistically, you are your own self contained organization. If you run the school, you are not bound by organizational rules. Now, for propriety, you may
choose to adhere to the promotion conventions of other organizations, but you are not bound to.
Of course, if you wish to operate under the thinking that KKW is real dollars and all other TKD outside of it is fake money, then I suppose I could do whatever I wanted.
As Puunui explained, plantation dollars, not fake dollars. Some stores used to issue store dollars, which of course, had to be spent at either that store or at a store in that chain.
Another way to describe it would be getting a 100.00 Visa gift card for your birthday. You can spend it in most places, as most retail stores take Visa. This would be your Kukkiwon certificate.
But if I receive a gift card or gift certificate from a local, independent retailer, then you would only be able to purchase items in that store. This would be an independent school's certificate.
Both cards are 'real' and both are worth a hundred bucks, but you can spend one most anywhere while you can only use the other at that specific store.
My hapkido and kumdo certificates are both essentially dojang dans. I have a TKD dojang dan and I also have a Kukkiwon dan certificate. The dojang-dans don't affect me; I teach privately and at the school where they were issued. The only certificate that would receive any recognition outside of where I train and teach is the Kukkiwon cert.
Daniel