2007-01-032022-02-032007-01-032022-02-03https://hdl.handle.net/11124/66682 copies. Text on verso, caterpillar proving grounds. Phoenix, Arizona June 1971.Date scanned: 2002-6-28.Held in the Russell L. and Lyn Wood Mining History Archive, Arthur Lakes Library, Colorado School of Mines.Donor: United States Bureau of Mines.A man in a hardhat stands with his back to the photographer, observing a piece of equipment traveling on a slope at the Caterpillar proving grounds, probably near Tucson, Arizona.Rights management statement available at: http://library.mines.edu/digital/rights.htmlCaterpillar IncMining machinery and equipmentPeopleStillImage