Thanks MP, a warm self congratulatory glow is suffusing through my one remaining brain cell, I will take up the challenge in the very near future, however earning some pennies comes first, so for the present, "Open House" must reign.
PS Having lived in Munich for nearly 3 years and visited the DM I realised that I have stood by the very machine and yet it was only when you kindly widened the view and I saw the wooden slip ring that the "pfennig schlagen Sie den Ventilator".
Cracking Museum btw.