You can add the year "1946" to the data for my trailer.  This is verified by the original title, and also by the California DMV in 2008 when I was able to have a "year of manufacture" license plate assigned to my trailer, a 1946 California trailer plate.  (DMV requires verified proof of year of manufacture, which was verified for my trailer by a licensed California vehicle verifier.)

 Thanks,

 Robert Bills