[RodB]

I'm in the process of cleaning a vernier dial assembly on my Philco 650 and decided to clean the brackets and metal dial hoop in the vinegar bath I was using to de-rust some metal pieces. The dial pieces were really gunked up. I was busy with company yesterday so I didn't get to looking at it till today. The vinegar had turned black. When I fished the parts out of the vinegar I discovered that the cross brace of the heavy wire hoop was gone. All that was left was the end pieces and part of the center hub. The remains were chalky and crumbling.

   

The one on the left is my spare, the right is the victim. There must have been a chemical reaction the vinegar had with the pot metal brace/hub that dissolved most of it. Just amazing. The hoop is nice and clean!