Hanno,
My first thought when seeing the data plate in the first picture was that it's an early cab 11/12 type plate, which would be out of place in a cab13...however, I am not sure when the switch from the old style data plate to new style data plate occurred exactly...it has to be somewhere in 1942.....my assumption was "simultaneously" with the switch from cab12 to 13, but there might have been a bunch of very early cab13's fitted with the old style data plate (?)
.....same question with the switch from old to new type description (8443 to C60448-M)....same time as cab switch?
Some of David Haywards research is posted here :
http://hotrod.gregwapling.com/chev-t...dian-chev.html.
the 1942 8443 is about halfway the page and David mentions both Cab12's and 13's.
sorry, this doesn't answer what "X2" stands for...
Alex