My source for a lot of these oddball items is
http://www.sportscollectorsdigest.com/mantlept8. The article just discusses the Mantle records but indicates that both were likely released in 1964. The version you have is the short printed version. At the time of the article--2009--it listed the price of the short print in the $100-150 range and the other issues in the $20 range. The author's pricing is usually pretty accurate. I pick up most of my items at a price close to his range.