so, I guess it was built after 1938...I had looked into the patent # also and never got anywhere...
Ironically I also have a Wilton 9400 that was bolted to an old metal bench in a saw mill that burned down back in 2003... I took it apart to clean it, etc... found a date of 11-52 inside... my understanding is that date is the end of a 5 year warranty period, thus it was built in November of 1947.. It'll be a nice smaller vise when I'm done with it...