US450971A Coalcutting machine Google Patents
Coalcutting machine . Download PDF Info Publication number US450971A. US450971A US450971DA US450971A US 450971 A US450971 A US 450971A US 450971D A US450971D A US 450971DA US 450971 A US450971 A US 450971A Authority US United States Prior art keywords machine track arm coal wheels Prior art date