Mark,
I'm sure you've discovered a bit of the history of the Mod 58 by now. It was originally targeted to police departments as a fixed sight duty gun that would elevate officers to more power than a 38/357 could provide.
They weren't successful in their intended use. In many peoples opinion, including my own, it was because they weren't offered with a light loaded "Special" type factory produced practice ammo acceptable to the average LEO.
I used a 41 Mag Mod 57 for duty and competition, the 58s all-target counterpart, and was always amazed the caliber didn't find more favor with law enforcement.
Several of us would buy Mod. 58's because the cost for the gun was ridiculously low. We would convert them to target pistols using 4 and 6" bull barrels and install Bomar Sight Ribs. We'd add a set of quality custom stocks or Pachmayr Grips and would have the sweetest shooting 41 Mags imaginable.
Today the 58s have become a unique and very collectible handgun. What you seem to have is a 58 someone took the time and effort to upgrade and personalize to a better functioning handgun. It may have lost some of its collector potential but who cares... I have a feeling your 58 shoots much better than the run-of-the-mill Mod 58...
IMHO, you have one of the "best bang for the buck" pistols S&W has ever produced... Enjoy it.......