There is a unique decal that was only used on Military Senior oil filters. Here is an ad copy from Popular Mechanics, June, 1943 that clearly shows the decals for both civilian and Military Senior filters.
This ad is VERY INTERESTING as previous research lead me to believe that the AC S-2 civilian oil filter was the 'descendant' of the Military Senior oil filter. That apparently is a questionable statement.
Note that difference in the civvy decal. The Military one is larger, and contains references to part numbers. The Civvy decal is simply a stylized AC logo.