Original 1955-57 GMC Truck Dealer Master Parts Book. This Parts Catalog [dated May, 1957] covers the Models 550 thru 970 H/D Trucks. This is what the Dealer used to order Factory Replacement Parts to Repair your Truck. It has Part Numbers, Group Numbers, Description, Quantity, Application and some Illustrations of the Replacement Parts that were available from GMC. It is in good condition for its age with normal wear, soiling and blemishing from use in a Dealership [see photos]. Very rare and informative tool for the GMC Owner or Collector.