For the T56X serial:
T = built at Tonawanda
56 = 1956 model year
X = regular production 235 from a 31-3200 series truck.
The X is only one of several possible suffixes for a 235 with that casting number, which could have been built at Flint or Tonawanda.
For the F401H serial:
F = built at Flint
401 = engine build date = April 1
H = Thriftmaster 235, used in the 31-32-36-3800 series trucks.
Though this serial number format (which changed in '57) doesn't give the year, the H suffix was only used for a 235 in '57.
What's your truck's serial number?
