You are correct, that gun is a civilian version of the Colt which was the standard service revolver from 1892 to 1909 in several different military model numbers.
A civilian gun would have the butt marked with the serial number in two lines, but nothing else from the factory except by special order. A picture would help a lot. The gun was probably made after 1903, since that is the year Colt removed the chamber shoulders to allow .38 Special* to be fired in that revolver. Prior to that, shoulders restricted use to .38 Long Colt (the U.S. service cartridge).
The four digit numbers are assembly numbers; the serial number should be on the butt in two lines. The grips should be hard rubber with either the word COLT in an oval or the rampant Colt in a circle.
The cylinder free-wheeling sounds like the cylinder lock (the part that fits into the front row of notches) is missing, broken or missing its spring. Few parts are available for those guns and few gunsmiths want to work on them because they are so different from anything else Colt made.
*Smith & Wesson introduced the .38 S&W Special in 1899 and, hoping for a military contract, made it the same case diameter as the .38 Long Colt mililtary cartridge, but longer. Colt would not put "S&W" on their guns and chose not to change their "COLT D.A. .38" marking, but public demand forced them to make their guns accept the "Special" cartridge, though they insisted in calling it the ".38 Colt Special" for a while. The cartridges are the same except the .38 Colt Special had a flat nose bullet.
Last edited by James K; January 27, 2013 at 10:33 PM.