Colt Army Special. Forerunner to the Official Police. Serial number dates it as 1919. Grips aren't original, of course. Army Special was just a Colt marketing ploy, the Army didn't actually issue these. Good solid revolver. Nickel finish may or may not be original.
Value on old Colt revolvers has been all over the place in recent years. Strictly as a guess I would probably start in the upper 300 range.