HIN
HUN51200M78G -25HUN is the manufacturers ID code. ( Hunter )51200 is the production or serial number.M designates "Model Year Format" (used from 11/1/1972 through 8/1/1984)84 is the model year.G is the month of production, February, using the Model Year Format Key.25 is not part of the HIN, so it is whatever the manufacturer wants.The early Straight Year Format is slightly different as is the New Format used since 8/1/1984.