From Simo Harkila:
The fender tag is read from left to right and bottom to top.
Here is an example from 1967:
the second and third row from bottom : below the S there is in my case a B. This "S" is the "stripe group" with code numbers between 310 -319 and 31B - 31Y. Only the last letter (or number) is printed, so in this case 31B is "horizontal accent stripe-black".(The stripe along the car side)
on the fourth and fifth row : below the X is #1 and below the Y is #1. The "X" is the "glass group" and the code 521 says "Glass-Tinted all windows". The "Y" is the "roof and top group" (300-309) there the 301 says "Convertible Top-black"