Keywords: history of technology historyoftechnology mining smithsonian probably public domain probablypublicdomain blackandwhite monochrome black and white SI Neg. CCC-2933. Date: 1/10/1929....Gear Shields At Machine Shop.Gear Shield at Machine Shop.From the Consolidation Coal Company collection, National Museum of American History...Credit: unknown (Smithsonian Institution) SI Neg. CCC-2933. Date: 1/10/1929....Gear Shields At Machine Shop.Gear Shield at Machine Shop.From the Consolidation Coal Company collection, National Museum of American History...Credit: unknown (Smithsonian Institution) |