MAGNET VALVES (Electro-Soupapes)                                                     

1. Very ancient model 
(Extracted from an authentic Merklin Pipe Organ)
2. More recent: Kimber-Allen valves 3. Very recent Peterson Valves
4. MERKLIN valve : note the cotton for isolating the wire, and the paper around the magnet !

The recent models, (picture 3) are much more compact.
Electro soupape Merklin

During a long time, Magnet valves had the form represented in picture 1
Wire were made with cotton, very dangerous towards fire risks. Support was on the opposite side of the pallet, taking much more room.
Some French "Organ Experts" are demanding mandatory to refurbish same magnets with cotton isolation ! Crazy !
(After official classification of them).