DJ, then SJ Vac Majors from late 1938-late 1942 (early 43?) are longer than those before and after.
However, Parker Canada had tough time following the "rules"
Long Majors (and even anomalous long single jewel Juniors) crop up mid 1940's from Canada, seemingly at random. Seemingly.
They tend to be about as long as the 1942 as-expected long single jewel USA-made pens.
david
http://www.vacumania.com