I believe all tracker bars originally had a thin coating of clear
lacquer.  My reason for this belief is this: I had a collection of
old parts, including a couple of old brass Duo-Art tracker bars.
They were stored in an outside shed for several years.  After years
of storage, I examined the old tracker bars and noticed that the
extreme margins had not tarnished, while parts of the brass where
the paper had worn away the coating, had tarnished badly.

I suggest one avoid paste or liquid types of brass cleaner, because
some contain acid and it is unavoidable that some of the polish will
entering the tracker bar holes.  Instead, I suggest a polish that
resembles cotton impregnated with a mild polish, called "Never-dull".

Once the tracker bar was highly polished and all traces of polish
buffed with paper towels, I masked the area, and gave the entire
tracker bar a very light coating of clear lacquer (not clear acrylic).
The tracker bar has remained very nice looking for several years.

Naturally some of the lacquer has worn off by the action of the paper
but the area where the lacquer has worn away is kept shiny by movement
of the paper roll.

Bruce Clark