My model 28 pictured is very close to yours in serial number, and exhibits the standard factory finish of the time.
That said, I have seen some variance in finish in model 28's, and like Jack said above, probably dependent on who was running the polishing wheel that day.
Still, one as shiny as yours is almost certainly a quality refinish. check under the grips, there may be a re-finish stamp if it was sent back to S&W for a high polish blue job.
Its darn pretty, and id be happy to own it.
Larry