you can't. why would you want to? just remove it, give it a good cleaning and spray it. (why don't you want the original brass? it will shine up beautifully. use 000 steel wool and BarKeepers friend or Brasso)

You can spray it with Rustoleum ORB metallic spray paint. I've redone my hinges with it. do light coats.

I agree with @Beth H. :, keep it there either polished up or not. I'd rather look at that than a flat plate. It's going to be like a record player sometime, what's old is new, even non functional,

Polish it up as suggested then perhaps put your house numbers on it.

its a charming nod to the past. the patina is wonderful, I would leave it as is and occasionally add a sign to it for some whimsy:

"Push button for housekeeping, if no one comes, do it yourself"

"Push button for free"

"Don't push this button"

"This button does absolutely nothing"

"POWER"

"complaint department push button for service"

etc..

I agree, polish it up and add some cute saying. It would be for fun.

Yall are too funny. i agree to polish it up and keep it and add whimsy if that is your style. vintage brass nutone ones on ebay are $150 and up so its definitely valuable and in demand. i think it looks better than my ring doorbell. i wish i was clever and could use this to make a cover for it.

note if its really badly tarnished it will be much easier to polish with a bench grinder/ polisher.

Love Rawketgal’s suggestions. We didn’t noticed the little round speakers in the rooms at first when we bought our house. They’re in the bedrooms, on the patio and outside (and above) the front door. The main control panel must have been removed or covered up since it’s nowhere to be found.