You have an early MkV Combat Master, and FTR that IS a "C" in the Serial Number,
not an "O". There were several gunsmiths there who when stamping SN's didn't get the "C" perfectly straight up and down and it can look like a washed out/buffed "O"; it's not.

Your pistol has a matching Matte Stainless Steel Slide and Frame, and both the described sights and grips are standard and original(that's a good thing).

Bummer about the "Dropping" of it, though they're pretty tough.
Value is between $450.-$600. currently and that depends a LOT on both where you are and how fast you needed/wanted the money if You're contemplating selling same.

Hope this helped,
--mick