Not much to add to what has already been said, except it should letter during the first half of 1904.
Thanks for showing the complete serial number; I was able to add this single action to my survey and database of when Colt really began proof marking 1st Generation Single Actions.
The only other observation I have, and I don't know if it is a photo anomaly, is the trigger guard bow appears to have been deformed along the bottom making it protrude downward, but that might just be an aberration.
Nice old single action!!!!