[WTSHNN]

Alright...

The Model A era badge was actually the Model T style radiator and was used 1920-1931.

This list that I have does not show what the letters designated for this style of badge but there is a comprehensive list for the later 1937-1960's era Rouge.
A - Motor Building
B - Motor Building, Paper
C - Plant, Tank Engine, Power Plant, Specialty Foundry
D - Gear and Axle
F - Engine Plant
G - Iron Foundry
H - Plastic
J - Exists, Dept unknown
K - Exists, Dept unknown
L - Stamping Plant
M - Iron Foundry
N - Glass Plant - under 5,000 Mfg Service, Over 5,000.
P - Casting Machine Plant
R - Steel Mill
S - Stamping Plant
T - Mfg Service
U - Exists, Dept unknown
W - Mfg Service, Under 5,000, Tool and Die under 5,000
X - Dearborn Assembly
Y - Exists, Dept unknown
Z - Frame Plant

This comes from a list compiled by a man named Jim Krucki.

-Tim