This book offers the most comprehensive collection of information known about marking gages. Included are detailed sections on: patented gages, manufactured gages, and unidentified gages. There are also patent diagrams, gage patent listings, and a reference list. The section on patented marking gages includes approximately 350 patents and many of their patent drawings. Details are given on the works as well as personal lives of manufacturers and patentees. A 16-page color photograph section offers high-quality images of 35 unique manufactured gages along with detailed captions. Hundreds of photos, line drawings, vintage advertisements, and illustrations pack this visual reference guide with valuable information, much of which has not been previously published. The material in this book is also useful to collectors of other tools; many of the manufacturers made tools other than marking gages. This is the first reference book of its kind for collectors and those interested in American marking gages.