The Gray Book is a good reference when trying to identify unmarked and older cast iron made before 1900. It was published in 2013 by Schiffer. It is designed to be a reference book. There are no prices in it. I find it a useful book. Pricing on the items shown in the book, like most cast iron cookware, is always subjective AND negotiable, especially when considering the condition or uniqueness of any given piece. Amazon and Walmart have carried this book in the past.