The total moving hammer head weight includes the anvil body, back spacer, back plate, top die and bolts, pivot bracket, pivot bolts and most of the lower linkage arms. These total 35 pounds.
The head body is a 4"x4" piece of 1018 steel. The lower linkage arms have bronze bushings and a zerk grease fitting. The lower link arm shaft is off center of the pivot knuckle. This will allow the lower link arms to reach almost a vertical positioned before binding.
The lower link arms are located on the fore and aft mass center line. This minimizes any forces not in the up and down direction of the head travel.
The bolts in the front of the hammer body are for fastening a handle to manually raise or lower the head from it's equilibrium position.