Usually the primary HIN is on the Starboard upper transom. The "hidden" is under the eyebrow.
After August, 1984 the HIN are thus:
First three letters relate to the manufacture. C Dory has had a number of different Manufacture Identification codes used for C Dory boats that I know of: DOR, CDO, GXK, MFN, CCR, UWH, MEH, CMC, (several of these are the Venture/Cape Cruiser) The next 5 digits are the serial number. Usually the hull length, and then build number, maybe not in sequence. Next is a letter which is the month of the year and a digit of the year of certification or manufacture. (Usually when the hull is started) Finally two digits model year.