Thanks for all the useful information. Alas, I can't post a picture, but I can confirm that the serial number that appears underneath the barrel when the cylinder is open is indeed 4623xx. The left side of the barrel reads "+ Officers Model 38 +"but does not say "Target." The top of the barrel reads "COLT'S PT FA MFG CO HARTFORD CT USA on one line, with PAT'D AUG 5 1884 JUNE 5 1900 July 4 1905"" on the line beneath it. Barrel is definitely 7 1/2 inches, front sight is adjustable for elevation, and the rear sight is adjustable for windage, with reference marks scribed next to it on the topstrap. Trigger is blued and checkered, and the backstrap is checkered, although I don't know if it was done by hand. Grips are checkered, with a silver insert bearing the Colt logo. I spent the afternoon yesterday cleaning dried oil and powder residue from the lockwork, and many of the parts appear hand polished and shiny once the gunk is removed.
Does any of this information confirm a manufacture date in the 1920s? Also, does anyone know how to actually adjust the sights? The rear has a tiny screw on the top and also on the right side; the front has a tiny screw on the muzzle end and another on the right side. Thanks again for all the info!