It seems to me there's a very simple explanation: he wore two rings. He being Oswald and not two different people (really? they used two different people to stage two photos?).
Two rings. Ring #1 was his wedding ring on his right ring finger.
and Ring #2 was his Marine Corps ring on his left ring finger.
Two different rings; two different fingers. No switching of rings. It's clear to me they are two different rings. One a wedding band and another larger one. My late father was in the Marines and he had one although I can't remember offhand if he wore it with his wedding ring after retiring or not. I seem to recall he didn't. It's kind of gaudy.
In the arrest photos he is wearing the Marine ring but not his wedding ring. He left that behind the morning of the assassination.
