Yes, I was able to loosen all the 14-mm bolts around the perimeter of the pressure plate. I cannot recall of there are six or eight of them. I got all of them so loose I could twirl them with my fingers. The pressure plate remained stuck in place.
My next plan is to wire brush all around the perimeter to remove external rust and corrosion, although not much of this is evident. Then I shall douse the perimeter in penetrant or vinegar (vinegar being the best rust-busting penetrant I have ever found albeit slow-acting). Maybe wait awhile and then apply the blows to hopefully jar things loose.
What is your advice if this does not work?
1959 M-B 220S cabriolet