I just did a search of the message board on Brads41-46Chevys site. Someone had requested decoding of the following serial number: 9OS09-2076. That's an early '46 and it's using the numerical month code, which is also out of the '42-'45 sequence. So the numerical month codes went thru the early '46 models, and the sequencing started over.
This site also has info on the Art Deco trucks. He mentions the month numbering system for '42-'45. He also mentions that the '46 first design started production on 9-1-45 and went thru 4-1-46, not the 9-1-46 that the '49 Truck Data Book says (must be a typo). That does seem to make more sense, since the '46 second started on 5-1-46.
