Hey Fighterpilot,
Some aquasports have a metal plate hidden under the rub rail with the hull number. They did that so that if the boat was stolen and the hull numbers eradicated, you could still prove that it was your boat. Don't know how many they did that way or in what years but the last 17' AS that I had needed the rubrail removed and I discover the id plate during that process. I'm not suggesting that you remove the rubrail but if all else fails, you might be able to loosen it a little and see if there is one on your boat. Mine was on the port side near the stern.
Keith