Original magazine ad - "Why all three models of Cat Tractor-Scrapers in our fleet?" Featured are 3 models of CAT tractor-scrapers: Model DW21 Series G - 345 hp, 22.6 mph Model DW20 Series G - 345 hp, 35.8 mph Model 619 Series B - 225 hp, 30.2 mph The scrapers shown are owned by Gordon H. Ball, Inc., Danville, Ca, with endorsement comments by Mr. Gordon Ball, Pres (pictured).