Well, I think I'm pretty well done ruining the patina on the Parker.
I used a 36 grit Cubi II fiber disk to rough the jaws even with each other, and, as much as possible, flat and square to what they need to be square to. I went as far as I felt I needed to, but, as it is, the vise is now a 954 3/8". If I took it all the way to flat and pitless, it would be a 4" vise--if that. I followed the fiber disk with an 80 grit flapdisk.
I've just started draw-filing the tops of the jaws flatter and squarer. I'll be working on that for days. I chose to not reprofile the jaws to the original rounded shape, as a flat top suits my needs better.
It's found its new home:
Of course, it didn't fit the studs I'd welded on for the $60 5" Palmgren that used to live there. I had to cut them off and weld new studs in. I made the mistake of using 5/8" all thread for the studs--I should have used 1/2". As a consequence, I'll have to drill the studs out from underneath to remove the vise from the plate.
All that's left now, after I finish the draw-filing, is to make some copper jaw covers for it. Maybe I can modify the ones I made for the Palmgren? We'll see. It's too hot to even contemplate annealing 2" copper pipe in the shop right now--92F.