Spot on harv, this block is very heavy i can not pick it up on my own. These blocks where used when forge welding bars and rods together they would use the shape to bring the weld back to the parant shape.
At one time i had it on the front of a Ford Super Dexta to hold it down.
I will get some more pics tomorrow, just at the moment i am nice and warm inside, its winter down here.