The answer to any question concerning repair or disassembly is find, obtain one that works or suits your cosmetic visual standard.
I had one in a condition to allow stubborn curiosity to investigate how they come apart, free of the fear of breaking anything.
The three holes in the bottom are nothing but drains, no trick release access to pushing any clips. As is typical, some expert bozo posted that. No idea why.
For anyone possessed, unwilling to accept the simple answer stated above,... The mirror pops out, step one, by itself. Careful, gentle prying releases it from an adhesive blob holding it to a plastic base.
To see a vinyl cover over the electrics, motor, wires, connectors, as a moisture seal. Old, fragile, thin. Long shot saving it intact.
After that, a person not put off by removing wire connectors, having to replace them or the old cracked wires, can suit themselves in the quest for victory. All necessary for total disassemby.
My initial motivation was cosmetic. Pitted chrome, removing, refinishing, sanding to primer, paint, no taping around the plastic frame.
Never mind. See topic paragraph.