Danny, one important omission from your list is the German Muzzle website: www.muzzle.de/N3/Druckluft/. Great source of detailed information, though in German, with numerous pictures.
Thank you, John. Now added.
Vintage Airguns Gallery
..Above link posted with permission from Gareth W-B In British slang an anorak is a person who has a very strong interest in niche subjects.