Admiral 24A12x tuner part

[Tony F]

While going through an Admiral 24A12x set I was cleaning up and re-lubing the tuner. I noticed that the "fine tuning" wiper had a gap of about 1/8" so that there is no contact, thus no fine tuning. Looking at another tuner, it looks like there is a highly polished metal disc that is either bonded or soldered onto the exposed metal piece shown in the pictures. The one that was in here is long gone. Has anyone come across this before ? Was it soldered on ? or do I need to obtain an entire piece from another tuner. Looks like I'd have to drill out the 2 rivets and replace the fine tuning "button" assembly in order to make contact with the "wiper" again. The square aluminum metal retainer has been removed in the pictures so that I could get a picture of the "disc" wiper area.
Thanks, Tony