My sister asked me how to tell value/ model.
The "F" under the serial number is a factory inspection stamp.
There should also be an inspectors stamp on the left-rear of the trigger guard web, and a Colt Verified Proof stamp of a tiny "VP" in a triangle on the left-front trigger guard web.
A thinned or missing "VP" stamp is a good indication the gun was re-polished and refinished in the past.
Value drops fast for a reblue.
The Army Special was made from 1908 to 1927 at which point Colt renamed it as the Official Police and made it until 1969.
All later Colt medium frame DA revolvers up to 1969, including the Python, used the same action and frame size as the Army Special.
Value depends entirely on the following:
1. Being in original configuration, with original grips and finish, no reblue.
Hard black rubber grips were replaced by wood grips around 1924.
2. Being in correct working order and timing.
3. The amount of original finish still left by percent.
Here's a general ball park value spread:
For a year produced use the lookup data base on Colt's site, or use Proofhouse.
The serial number is stamped on the frame under the barrel where the crane seats and on the crane opposite the frame number. Often the number is also stamped inside the side plate: