Hi Russ, sorry to be away so long. We had a death in the family last fall, then the holidays, etc and been busy plowing, work, etc. Anyway, I will take a look at my backhoe as I don't have much in the original service manual I got with the tractor. I know the loader is a Davis 102 that was factory installed and I have some info on that but the backhoe was probably added later.
In fact the seat is on the tractor not original and I think it had to be removed and replaced with what I have in order to make room for the backhoe. My seat is kind of mickey-mouse as it just sits up a little higher in a round tube someone welded onto the tractor. It works OK as I can either just sit backwards in the seat if I'm doing something quick with the hoe or I pull the seat out and turn it around to face the back of the tractor if I'm working with the hoe for a while.
Other than that the hoe is awesome, very strong and heavy duty. My brother-in-law who is a landscaper was amazed at how big the hoe is and said none of his bigger, newer Kubotas have hoes nearly that heavy duty (same for the front loader).
I will go look for some numbers or other ID info on the hoe when I can but I haven't seen anything obvious on it yet.