On this pic, which gear is made by whom?
As a another side note: Fenner-Stone used to have relief ports leading from the shaft at the seal and from other area. (I'll need to go and find those pump heads to see). Kind of like what we see in the pic above, but they were drill and not slotted. Anyways, I tapped out those ports and installed set screws to stop/slow the fluid leaks. This appeared to be a bad idea. The pumps seemed to struggle or bind or something.
One day I decided to block off all the ports on my block with a pump head (gears, same thing) bolted to that block. I then got another complete pump, (gate) and connected the pressure hose from that pump to the inlet of the gear head that was bolted to the block. Hitting the switch I could see all the areas of leakage at the gear head.
From this I learned that those early Fenner pump heads leaked like crazy. Machining the shaft guides to allow the use of o-rings to prevent leaking and using a plate over the back end improved the inches. But blocking the relief ports was not a good idea.
This brings us up to todays pump heads. Of course we don't see the external leaking, but, I wonder if the internal designed fluid relief is made for life and not performance. As I have yet to take on and study these new pump heads up close and personal.