I would see A. The cloned me in chamber B would be brought into existence at that moment. They would share all the memories as me, and believe to be the one in chamber A. May be slightly confused about why the letter changed, unless you prepared yourself beforehand.

But the original observer that was put into the duplication chamber, would maintain their letter A

If consciousness is purely a result of the arrangement of the brain, why would you not see B and the copy see A since the bodies are identical? This paradox is the problem with a simple emergent property explanation.

To say somehow the different history of the atoms in the original brain vs the atoms in duplicate is somehow relevant to the emergent property would be a very odd claim: we don't take into account the prior history of the atoms in turbulent flow for example, just what the are doing right now.

Or for clarity, if I gradually replaced every molecule in your brain with another identical one, the emergent "you" would not be affected. So, if it weren't already obvious, it clearly can not be dependent on the particular atoms that make you up.

And by the way, if your brain at 10 years old and 90 years old, in spite of being very different structurally, still give rise to your same "you", the copy would not even have to be very good.

It is a fun problem I must say.

I'm not thinking about this from my perspective, however. I'm in a way thinking of it from an outsider's perspective.

In terms of "me", there would be two individual instances of me that open their eyes and either see A or B. The "original" is determined by you the question-asker, and the fact that that "original" walked into chamber A. Because that "original" walked into chamber A, that "original" would see the letter A, whereas the clone would see the letter B. Its possible that the "original" was, at time of cloning, completely recreated/rearranged. However, that "original" would retain the A designation/"originality" because to an observer, someone walked into a chamber with no other exits, and exited out the same chamber, that someone is the same person.

You are as much what others think of you as what you think of yourself, in this case.

I don't think this as mysterious a problem as you think it is. If I take a snapshot of a VM on aws, and copy it to a new instance, the vm will 'experience' being shut down on one instance and waking up on another, while the original will wake up exactly as it was. This no more negates the existence of the operating system than your scenario negates the existence of consciousness.

(Btw, the videogame _Soma_ goes over your exact scenario)