Your date code is too long. Should be 3 digits ie..16D 0r 10J. Going by what you have there, 16D would equal April 16, 1959. 10J would equal
September 10, 1958 . It is fairly asy to decode. The Day comes first, then the month. You have to eliminate the letters "I" and "o" because they can be confused with "1" and "0". You count the position in the alphabet that the letter is and eliminate either of the above if the come before your letter. Whatever number you come up with would equal the month. It can get confusing.