Keywords: Holt tractor-type patent.png Holt Machinery Company patent for a track-type tractor number 1076578 Filing date 18 Feb 1913; issue date 21 Oct 1913 http //www google ca/patents id NTdvAAAAEBAJ U S Patent Office 1913 PD-USGov 1913 drawings Holt tractors Agricultural machine illustrations Technology in the 1910s U S Patent drawings |