| http://www.w3.org/ns/prov#value | - rilling rig mast; a first piston and cylinder subassembly pivotally connected to said mast for pivotation about a horizontal axis between a vertically extending, inoperative position, and a horizontally extending, operative position, said first piston and cylinder subassembly including a cylinder, a piston mounted in the cylinder, and a piston rod projecting from the cylinder and connected to the
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