Going through my CCKW manual (doesn't everyone reread the TMs on a monthly basis ?) I happened to be reading the "Assembly Operations GMC Trucks 6x6 Two-Unit Pack" and while the manual has not date, my best guess is that its a late 1942/early 1943 edition by the fact that it still goes by 'Yellow Truck & Coach' which was bought out in mid 43 by GM.
I found that there are two distinct types of oil filter body labels.
Here is what I am calling the 'Early' decal:
Here is what I am calling the 'Late' decal:
Here is what most places are selling. I call this the civvy decal. This is a 2in diameter decal.
Note that:
The Early decal is round, is just the AC logo and part number.
The Late decal is oval, contains a smaller AC logo, clearly states "Use Senior Element" and part number.
The civvy decal is just the logo.
My educated guess is that the logo changed in early mid 43. This would coincide with the CCKW becoming standardized to use common military parts, not vendor specific parts.