My 928 had its original 'flag' mirrors removed by one of the previous owners. They made a good choice, in my opinion, and added these really cool, later model, 'aero' mirrors. But, they did a poor job and didn't wire them up properly, or use the correct gasket to keep them sealed, and they even decided to skip wiring altogether and snipped the wires. So, I am now trying to get the mirrors apart so I can clean and rebuild them to work the way they are supposed to. I have gotten them off of the car, and taken the base off, but the glass really does not want to let go!
You can see in these pictures why the gasket is important, all of that dirt... They did try to seal it up with something like caulk, and that should be fun getting off the doors.