related tags: 1930s 5A5451 A6A4A3 A8A4A1 BDBBBA BFBBB8 D5D3D3 D6D3D2 ECEBEB belttripper blackandwhite bw construction equipment iron ironmountain linkbelt minnesota oliverironminingcompany ore stockpiling vintage 1938 1950 575453