One more thing: you rely on A and B not keeping and later combining those private key parts.
You're right. I didn't mention it because I thought it's obvious, and unavoidable. Funded collectibles are just not compatible with "verify, don't trust".
That would require destroying the hologram?
Or the designer keeping the partials.
Person A makes one part, Person B makes the other part. They don't know each other's data, make the collectible coins, and sell them. Everyone's happy!
8 years later, Person A meets Person B again and start talking. Person A just got divorced and lost his house. B has gambling debts. They start talking about "what if...." and it turns out both kept a backup. They join forces and empty all collectibles they ever created.
There is no way to avoid this other than trusting both A and B. Or better: you
can avoid it, by not trusting any of them.
My question is does your system keep/store any data?
The answer to this question doesn't really matter: you can't verify it. A honest person would say "no", but so would a scammer.
Being closed source, there is no way to validate what it does - so thst requires us to trust you and trust the creator.
Open source software doesn't help either: you still need to trust a person.
Technically, if there’s only one private key that exists, and it sits under a hologram of a coin that you own, then the key is yours and yours alone - unlike an exchange that actually holds your btc for you.
Unfortunately there’s no way to know this with certainty, so the sentiment here is correct.
Let's call it Schrödinger's key: it may be yours, but at the same time you may have nothing or someone else may have it too. You can't know for sure until you open the box.