I found this relic in a box once belonging to a very thrifty man. He would not buy a tool ever if it was possible to modify another on the cheap. Him and I both having worked heavy diesel, I think he made this to remove hydraulic pumps from the bellhousing of the older D8 Cat crawlers.
It is a GRAY 729, also marked FORGED STEEL, badly worn over the years.
Liberal use of the torch with a little weld to fill in voids, finished with a lot of filing and sanding. I did not try to get it perfect because I like the look it has, well used but cared for.
The 5/8" end has been opened to 17mm, another mod by him to fill a gap in his tool kit.