I never thought much of post drivers until I saw a video from Australia of a post driver pounding in concrete fence posts. The posts had a cap on the top.
Yes.....it works fine! I actually purchased a Shaver HD8 driver at the same auction. The shaver is much lighter duty, but also has a way faster downstroke. This BEAST has a huge cylinder and weighs about 1500#!
I found a JET driver and appears to look similar.... due to the ballast type weight boxes....but I cannot find any good brochure pictures or videos of that unit in action.
I'm really thinking it was not home built.....rancher modified perhaps?