The (Official) Overstreet Comic Book Price Guide, first published by Robert M. Overstreet in 1970 as one of the earliest authorities on American comic book industry grading and collection values. Overstreet sold his company to Gemstone in 1994, but continued to "serve as author and/or publisher of Geppi's Entertainment Publishing & Auctions' line of books." Publication of the "Price Guide" was taken over by Gemstone in 1998, Gemstone took over publication, and the twenty-eighth edition to the present have been (co-)published by Geppi's Gemstone publications. The "Guide"'s 39th edition was published by Gemstone Publishing in 2009.