I found this on a daysailor forum.
QuestionI own a 1967 O'Day Day Sailer. It has the original O'Day data plate in side on the forward wall of the cuddy. It is engraved with a hull # of 15344 and a class # of 2724. Since this boat was built before hull numbers were required in the fibreglass and I have registration documentation back to 1972, with the boat registered against the hull number, I believe the plate has not been altered. Does anyone have an explanation for the high hull number. I have been told that O'Day tracked all of the hulls it built (regardless of type or class) by the number and assigned a class number that represented the number of boats in that class. Also the class number is the number that should appear on the sail. AnswerBefore the requirement for the 12-digit Hull I.D. Number, O'Day gave every boat 2 numbers, a Hull# and a Class#. The Hull# represented how many total boats O'Day had built, and the Class# represented how many of that Class O'Day had built. So your 1967 DS I was the 15344th boat that O'Day built, and the 2724th Day Sailer. If there is a number on your sail, it should be the Class# 2724. This was O'Day's method of serial numbers for their boats until the 12-digit HIN went into effect on November 1, 1972. I added the link.Does that help?