Vacuum Booster plating Color

[cdn454LS6]

I know this thread has been talked about before but I can't find it. 1970 chevelle LS6 Earley Car Leeds Plant,I have a survivor engine compartment and the brake booster for some reason was painted black..I stripped the black and underneith found dull silvery gray with 5-10% of Low lusture gold, Has the usual light rust from the master on down.
Should I leave it or plate it, and if I plate it is it the high or low gloss gold or more of the silver/gray. Any help would be very much appriciated.
Thanks very much.
Ken