Picked up the '64 220s

You can easily tell early chassis VS late, or 1st version vs 2nd version. Open the hood and look at the middle of the firewall above the engine. If there is a flap that you can open, it's a 1st version. Otherwise it's a 2nd version.

2nd version cars have a regular power booster, dual circuit front disc brakes. There are also minor front suspension differences.

1st version have drum brakes and no remote brake booster or front disc with a remote brake booster.

The service manual refers to the versions.

My 1965 220S is a second version.

You will have to take off the door card (cover) and oil the screw threads from inside. You can also try some freeze spray from Locktite, for instance, and a hand impact wrench.

A 50-50 mix of ATF and Acetone is a good lubricant for loosening stuck threads. Let is soak for a few days and re-apply often.

You can remove the rear door hinge pin and the door will come off, but the screws will still be attached.