This is a steam hammer of the type used in heavy industrial workshops for forge work.
The hammer head is powered by a double acting fixed cylinder, 1" bore x 2" stroke. The cylinder has a slide valve, controlled manually by a lever through a linkage. The hammer head is fixed to the end of the large diameter piston rod and acts against an anvil fixed to the base. By means of the lever, the operator can raise the head or force it down against the anvil.
As acquired, the hammer was not in working order. The piston was too stiff to operate with either steam or air. After dismantling and cleaning internally, it worked sluggishly on air but not on steam. The piston was made of plastic, which was probably not original and probably not a good idea. I have been able to source a replacement piston and it now works well.