The goodyear date coding system from back then is well known and published all over the internet:
First digit (Year)
M or Z = 66
K or Y = 67
L or T = 68
J or U = 69
E or W = 70
H or X = 71
G or S = 72
Second digit (Month)
T = Jan
U = Feb
F = Mar
S = Apr
Y = May
N = Jun
P = Jul
A = Aug
C = Sep
K = Oct
E = Nov
R = Dec
Before the standardized DOT date coding systems started, each tire mfr. had their own system and all of them were designed to make it impossible for the consumer to decode without having insider info from the mfr. That way stock rotation at the tire store didn't matter!
Tufsyn was the name of a type of Goodyear rubber (see this ad:
https://www.ebay.com/itm/35399373316...evt=1&mkcid=28 ). And Packer has something to do with one of their very early rubber chassis products (I researched it several years ago but don't remember the details now, seems like it was some sort of bushing).
So for the month they were using letters that meant something to them in house, but would mean nothing to the consumer!
Now, don't ask me where in the world they got the system for the year. Makes no sense to me!