Many Iver Johnson and U.S. Revolver Co. revolvers have a visible serial number on the trigger guard, under top strap, or bottom of butt. However except for earliest guns, the "real" serial number is hidden on the grip strap under left grip panel (or one piece grip), with a letter prefix to...
From the picture I know that it's chambered in .38S&W, it was made sometime before 1909, the 5" barrel was a factory option, and it was designed for use with black powder ammunition.
I don't remember off the top of my head when they started using a letter prefix on the large frame Model 1900's but I'll look it up tonight.
According to the book, if there's no letter prefix to the serial number under the left grip (shouldn't be one based on the direction of the owl head on the grips) your revolver was built in 1902.
If there's an "F" prefix, it would be 1911. There was also a "C" prefix on the large frame Model 1900 but the numbers stopped just over C20000 in 1941 so it's not that new.