I just took a closer look at your pictures.
What I see is a fine specimen of a Pinnacle that looks great for 25+ years of exposure!
Most of the discoloration is where the bolts rusted and left rust stains.
As for the "oxidized" or dull finish, that may well be "factory".
The faces of parabolic reflectors can't be painted with glossy, as it would reflect sunlight onto the LNBF at certain times of year.
It is very possible the factory used -flat- powder coat on everything.
Before I go any further, let me express strongly that I would do NOTHING to the aluminum dish/ribs/panels!
...other than wash 'em.
Now, as to the mount, it IS in excellent shape.
Whatever it is coated in, has performed beautifully in 25 years of service.
I might be tempted to see if I could just get off the surface stains and leave it at that.
Damaging the integrity of the existing coating might be a mistake.
I can maybe see replacing the bolts with stainless, if you don't want 'em rusting in the future.
Let's hear from other Pinnacle owners on the conditions of this dish, and what work it needs.
