Quarrymen in Suits were the real Swingers

I believe that I am looking at a steam driven swing hoist – standing on its own, its function was to control the side to side movement of the derrick boom.

Cape Ann Granite quarrying never progressed to the point of an enclosed boom derrick operator shed, from which all aspects of derrick movement and lifting could be controlled by a single Hoist Engineer who followed hand signals relayed by the Derrickman.