23 REVOLVING POWER-SHOVELS, DRAGSHOVELS, CRANES, CLAMSHELL EXCAVATORS, DRAGLINE EXCAVATORS, AND BASE MACHINES (COMPRISING REVOLVING UPPER AND NONREVOLVING LOWER WORKS) FOR SELECTIVE MOUNTING OF VARIOUS TYPES OF BOOM (INCLUDING SHOVEL BOOMS, DRAGSHOVEL BOOMS, CRANE BOOMS, AND THE LIKE) ALL OF THE FOREGOING BEING CHARACTERIZED BY HAVING A RUBBER-TIRED WHEEL-TYPE ENGINEPOWERED MOBILE LOWER WORKS