This is cambridgeorganists.org Designed and produced by Stephen Taylor for the Cambridge & District Organists’ Association
No 17: Organ Leathers
A surprising variety of leathers is available for different purposes.
The most useful is white split sheepskin used for bellows and stopper lining, but differing thickness, strength and pliability determine different applications.
I obtained this sample swatch some years ago when I purchased leather to reline the stoppers on a stopped diapason.