Two links that may be of help:
http://benoit.suaudeau.perso.neuf.fr...am_prontor.pdf
http://www.rolandandcaroline.co.uk/r...prontors1.html

the delay mechanism in Prontor and Compur shutters are wrist watch type mechanisms employing a spiral torsion spring not a straight arm torsion spring as most shutters do. these type shutters require a more refined service technique than the conventional ones.