A lot of early HINs did not seem to follow the standard exactly. My own 1979 conforms very well: HUN37074M79H is a Hunter 37, #074, 'M'anufactured in 1979 on month 'H' or March. But that means that the boat was built in March of 1980 because the 'boat year' begins in August or so I have been told. So your boat #180 was built in 'J' or May of 1977 . . . . maybe. No idea about the '2' or why '50' instead of '25'.