This is a very nice, honest, early example (two line patent declaration ending June 5, 1900) of Colt's largest frame pistol, chambered in .38-40 Winchester, one of the classic 19th century rifle/pistol calibers (.38WCF).  An excellent shooting New Service in it's original scarce caliber. 
  The hammer and trigger show some nice color, although the blue on the rest of the pistol seems pretty faded or gone on wear areas such as front grip and back strap.
  Absolutely NO rust, NO pitting, and a really nice bore, just very thin blue but for hammer and trigger.  (see pics)
  The most unusual/striking feature are the genuine composite ivory grips with genuine Colt medallions which are pre-war (I've got a little provenience documentation on ownership going back several decades) and to me at least look way better than the photos show.  Very nicely mellowed.  Sadly the inside (left)grip has been chipped from a bad drop decades ago. More visible in the pics than live, but it's there.  Practically unnoticeable when holstered on your hip (which I've enjoyed).  During most of the time that I have owned this revolver I have had the walnut grips on it so as not to further risk the ivories but no reason not to, your choice.