Bosendorfer capstans

[David Graham]

I'm working on a 1920's Bosendorfer, replacing hammers and shanks.
The wippens are original, but in remarkable condition. However, I'm
stumped by the capstans. They are a dark gray. They do not change
when polished with a buffing wheel, so they aren't just tarnished.
Anybody with experience with these pianos? BTW, one of the reasons I
didn't replace the wippens anyway was that the Renner replacement
had a wippen heel that was about 1/4 inch shorter than the originals,
which puzzled Lloyd, and the jack angle was also different.
David Graham,RPT
dgraham@byu.edu