[Alan Douglas]

I would stick to chemical methods rather than abrasives. "Oven cleaner" is a bit of a puzzle, as brass tarnish is normally removed with acids such as sodium bisulfate (was and I presume still is sold as "Sparex" for jewelry work; also was in toilet-bowl cleaners but I always used Sparex).

These plates seem to vary, but if the background is supposed to be darker, it may not be after cleaning. They don't look that bad to me. How are the tuning-dial escutcheons? Those are more visible. If they look good, and the panel shines, nobody is going to notice the small plates.