Amazing book. I love looking through and seeing the 1908 prices, such as a grand piano for $198 or a spade shovel for 98 cents! Here are the insulators they have listed....Single Groove Pony Insulators, 400 for $6.30 ; Double Groove, 400 for $6.30 ; Porcelain wall or fence post insulators, 100 for 42 Cents! Amazing!