Here is a nice lot of earlier reference books.

Gerald Brown: Collectible Porcelain Insulators, 2nd ed. with supplement.

Tibbitts' A Guide for Insulator Collectors. Vols. 1-3

Frances M. Terrill: Rare Insulators with Prices, and Hemingray Insulators Priced.

Most show very little wear. I am asking $30 plus media mail shipping for this group.