i think the first batches of them said" police carbine", but sturm ruger didn't like the idea of rifles sold to the public that said POLICE on them, so they changed the stamping to "ruger carbine" instead. If you research the serial # on yours and get an early model date, then it MAY be worth a little more to a collector of these rifles, but i doubt it would be worth much more than an extra 50- 100 bucks?
( Unfortunately parts are impossible to find for these, so if yours is not in great condition, it would be only worth parts to somebody in a few years)