Welcome to the forum!!
I was sure one of the Colt guys would be along to answer your questions, but they seem to be elsewhere. I'm not much into Colts but I will give it a try..
First off I can tell you what it isn't. It's not a M1889 Navy. It is what is called a Colt New Army and Navy Revolver. The problem is that there are 6 variations of this model (M1892, 1894, 1895, 1896, 1901 and 1903) and I don't know how to tell them apart. The other problem is that many of the earlier ones were upgraded to the later one's specs. The Navy variations show as having a lanyard swivel as standard and I don't see any sign of where one was on yours. Also they normally had wood grips. However, one thing different on yours is the "WBW" mark on the butt. This is where the inspectors initials are and, as far as I can find, WBW stands for "William B. Whittelsey, Lt. USN" who was an inspector of Winchester Lee 6mm Navy rifles at the onset of the SP/AM War. ???????
I'm guessing it's a M1895, but that's just a guess.
You might try posting it over on the Colt Forum (www.coltforum.com
). There is an expert on the early Colt DA's there.