YMMV but it was fairly typical back in the day, with Italian bikes at least, to polish the metal on parts that were going to be exposed like lugs, fork crowns and the ends of the stays and fork tips and then chrome the entire frame, for corrosion resistance presumably. Only the parts where the metal was polished prior to the chrome plating process really shine. The rest would have a dull and somewhat rough or scratchy silver finish. If that is the case you can't polish that. The layer of chrome is extremely thin and does not fill the surface imperfections in the metal. Of course I guess you could get lucky and they polished it all so you'd have to check on that.