To identify a factory original finish on a Colt 1917 take a look at the area surrounding the front sight. If you see a section that appears to have been taped off with a smoother polish than the rest of the barrel, you have one with an original finish. This is where the solder was cleaned up after the front sight was installed. I you look very closely at this pic you can see the outline next to the front sight. As mentioned earlier, the Colt's didn't have the "commercial grade" polish jobs that the S&W 1917's had.
Many 1917's were re-furbished by the Army for service in WWII. These guns have a Parkerized finish, and include additional inspectors marks.
The Colt's are suited to larger hands, and have a bit longer trigger reach IMO.
My personal 1917 has virtually no original finish left (except in some protected areas), was not re worked for WWII, and has all it's original inspection marks intact, sharp and clear.
At nearly 100 years old (shipped the last week of 1917) it locks up and times exactly as a Colt should with ZERO play.
Although the trigger pull is quite heavy, it's smooth as butter, and is probably the most accurate revolver I own. Shoots 230gr ball perfectly to the sights. My friends call this one "The Lazer" due to it's accuracy.
Clearly it's seen some hard use over the last century, but functions exactly as it should.