Could the first two digits be the day of the month, the next character a letter representing the month, and the final letter the year starting with 1969...
12JB = 12th day of September 1970 20JB = 20th day of September 1970 12JA = 12th day of September 1969 14LA = 14th day of November 1969 19FB = 19th day of June 1970 27MA = 27th day of December 1969 5MA = 5th day of December 1969
