I was trying to clean my Matthias Vise. It had a little surface rust in a few spots. Was having trouble removing it. Someone suggested "naval jelly". It took the rust, alright, and the finish as well!
I was devastated.
I contacted Rich Matthias who still makes his vises, although a bit modernized from my mid-90's version.
Anyway, here she is. Arrived today. He switched out stainless for the original steel parts.
He re-finished the parts I had ruined. He gave me two new bobbin holding rods of stainless.
He polished all brass. He replaced the C-Clamp mechanism.
Anyway, he made her better than she was originally!

Great Service!