Keywords: history of technology historyoftechnology mining smithsonian probably public domain probablypublicdomain blackandwhite monochrome black and white SI Neg. CCC-3020. Date: 6/25/1931....Trolley Pole Machine at Machine Shop.Trolley Pole at Machine Shop.From the Consolidation Coal Company collection, National Museum of American History...Credit: unknown (Smithsonian Institution) SI Neg. CCC-3020. Date: 6/25/1931....Trolley Pole Machine at Machine Shop.Trolley Pole at Machine Shop.From the Consolidation Coal Company collection, National Museum of American History...Credit: unknown (Smithsonian Institution) |