Intake/outflow Faces:
On the pressure pump, the oil seal keeps the center of the inner rotor from rubbing against any metal.
Grinnin:
do you have any idea of the genre of the pump that had the dimples reversed, i.e., was it from a post-1975 bike?
What brings this up is: your mention of the seal ring wearing into the rotor. On all of the pumps I have, the seal ring is well-embedded into the body (makes it a major pain to remove) so it can't possibly touch the rotor, and on all the pumps where I have changed seals, likewise.
The pump with the dimples reversed came out of a CB750K5 manufactured in October of 1974 as a 1975 model. The engine number is much lower than the frame number.
I didn't write that the seal wears into the rotor. I wrote that the seal prevents the rotor from rubbing against metal. I .e. the seal DOESN'T wear against the rotor. The linear milling marks are clearly visible in the top right of the picture above.
I also make no claim that the pump was assembled that way at the factory. I only claim that most of the wear on the pump parts is easy to identify.
