Jack Todd, the creator of the U chart number system for porcelain insulators. Start with a hard cover 1971 "Porcelain Insulators Guide Book For Collectors" (used but in good condition). Add Supplement A (1972) Supplement B (1973) & Supplement C (1975). Next is the Second Edition of "Porcelain Insulators Guide Book For Collectors" (1976) like new condition. "A History of The Electrical Porcelain Industry in The United States" (1977) also in like new condition..."Insulator Patents 1880-1960" (1985) like new. Just a ton of information in these hard to find reference books. I'm asking $40.00 plus an additional $5.00 for media shipping. Check, money order or PayPal (friend).