Librarian, NMAH Branch Library,Smithsonian I think you might try the folks who publish "Crown Jewels of the Wire", a monthly newsletter for insulator collectors. This library subscribes to this and the extent of their knowledge on insulators is impressive. One can write to: The McDougalds/5N941 Ravine Drive/ST. Charles, IL 60175; their phone number is (708)513-1544; they published a reference work for collectors called: " Insulators: a history and guide to North American glass pintype insulators" and I think there are other such guides that the McDougalds make available.THey would probably be glad to help. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %Smithsonian Institution SI Libraries % [log in to unmask] NMAH 5016 Stop 630 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%