Boats made before
1972 did not require the current type of Hull Identification Number (HIN), which can tell you a lot about who made the boat, its serial number, and month and year of manufacture. In your case, it would appear the "MSZ" tells you the boat was made in Massachusetts as that is the Manufacturer's Identification Code (MIC) used by the USCG. The remaining numbers could be anything, but I would guess the last 3 digits mean you have hull number 797, but that is just a wag. These are nice little boats and very good sailors. Good luck with yours.