Not sure if this helps you in any way, but a “silver bath”, or “Silberbad” in German, would usually be a mixture of water, salt and baking soda that silver is dipped into for a couple minutes. I’ve done that with silver cutlery and it’s clean and shiny afterwards - I can’t imagine doing that to a dial, though. Even if the dial is solid silver, surely the printing would suffer from the aggressive baking soda (sodium bicarb)?