A great find, Regi! One of the top German piano makes and it looks like
that one is from a golden period in thier manufacture.
For 'capstan' regulation, there will be screws at the ends of the keys,
under the strips of action cloth, functioning as very low capstans.
I guess the felt pads joining the damper heads were conceived to give
some felixibility and aid in damper seating.
Once you;ve restored it, I think that will be a magnificent instrument.
Roberts Pianos in Oxford, England, have before and after videos of a
Grotrian Steinweg on Youtube. Here's the After one
https://www.youtube.com/watch?v=mqUygiV83Qw
Best regards,
David B.