WATCH POP

If the date stamp on the back of the case says N7, the it's 1967 and if it's M8 then it's from 1958, correct? I'm not 100% positive. Would that make anything manufactured in the 1940's start with an L, and the 1930's a K?
Thanks for any assistance!
BOAT = Break Out Another Thousand. If you have a bad day fishing, you can say "they weren't biting". If you have a bad day golfing who can you blame? *still own more fishing rods than watches, but the battle is far from over. N7=1977 and M8=1968
A=1940 (only used starting in late 40s)
L=1950
M=1960
N=1970
P=1980
T=1990
Prior to this period Bulova used symbols on the movement to indicate year of production. See this table:
from Manley Horlogerie