Triumph Serial # Year

I am thinking about buying an old Trumpet from someone. The Serial # is TRNJ5612. They do not know the year of it. I cannot quite figure out the Serial #. Do I drop the TR, and look at the N and the J for year and Month? Any help would be Great! Thanks in Advance.

 

I can’t answer your question fella, but maybe this can…

https://www.lowbrowcustoms.com/blog...riumph-motorcycle-engine-frame-serial-numbers