[Arran]

Those later Grebe models sure took a downward slide in build quality compared to the MU-1 Synchrophase of a few years earlier, pot metal may or may not be a problem in the frame of a tuning condenser, but making a linkage out of it is just asking for trouble no matter how sound the mix is. Even if it doesn't warp or start flaking apart it doesn't wear well. Fortunately it looks like they only used the pot metal for the end plates and used rods and spacers to hold the assembly together, used Bakelite or phenolic strips to mount the stators, and didn't use pot metal in the rotor portion either, so a Majestic or Crosley style failure isn't as likely. Even if they had been buggered up it may be possible to use an A.K model 40 style parts set as an organ donor since the caps are all single section and not ganged.
Regards
Arran