1969 Body Tag Data

If the trim tag has "S404" in what we call location H of the trim tag.
This decodes or means that on the 19th working day of the month
("S" is the 19th letter in the alphabet) that this Firebird was the 404th one
sent down the assembly line that day.
If your '69 trim tag has a letter, any letter of the alphabet, in this location
and it's followed by a 3 digit number then this is what that code means.

For those of you who don't want to count to your letter in the alphabet then here is a
list of the working day letter code meanings:

A=1, B=2, C=3, D=4, E=5, F=6, G=7, H=8, I=9, J=10, K=11, L=12, M=13, N=14,
O=15, P=16, Q=17, R=18, S=19, T=20, U=21, V=22, W=23, X=24, Y=25, Z=26