Cees Verschoor is best advised to read the book, "The Fairground
Organ", by Eric Cockayne, which was republished in 2001 by the St
Albans Musical Museum Society.  This includes four detailed cross
section views of keyframes, by Gavioli, Bursens and Hooghuys.  The
book also includes briefer details of how the keyless system works.

For more details of how an organ works one should read the book by
Herbert Juettemann, "Waldkirch Street and Fairground Organs", which was
republished in English in 2002 by Andrew Pilmer, ISBN 3-87885-249-5.
Figures 1.21 and 1.22 show the most common Gavioli system and Figures
5.18 and 5.19 show an alternative system employing an intermediate
valve.  The book is full of detailed drawings of keyless systems and
the internal pneumatic workings of the organs, much of which is common
on a keyed organ.

I believe both of these books are still in print and should be
available from any decent library.  The true enthusiast will buy both
books.

With best regards from Great Britain,
Nicholas Simons