You'll need the first 2 digits of the serial # to decode date of manufacture if there is no date code (letter) in the serial. From 1968-1972, the first 2 digits were the date of manufacture, after 1972 you subtract the first 2 digits of the serial from 100 to arrive at the date of manufacture. You can also use the list at
http://www.marlinowners.com/forum/ma...sheet-pdf.html to decode the date of manufacture.
Stu