I sent all my original Smiths guages to a rebuild shop I found in Hemmings Mtr. Nws. The proprieter was a crabby old bird who's work was impeccible
The guages returned looking brand new even though they had been installed in the car in 1960.
Rock steady on both the tach and the speedo while the
oil prsr., vlt mtr., fuel guage and temp guage performed flawlessly. They cleaned the faces as well as polishing the bezels and the lenses.
I think I paid about $150 for the checkout/repair job. I never had a single problem with any of the guages after they got the once over.