Thanks, vrooomed! The visual aid of the forty different backs (Super Bowl XII in the Superdome) is super helpful for variation hunters.

The backs of the stickers (insert set) complete a puzzle in 40 pieces. There are variations where the same fronts of the stickers will have different back puzzle pieces. While not numbered, I have designated them by row (numbers 1 thru 5) and columns (letters A thru H), starting in the upper left corner. Thus the upper left corner puzzle piece will be designated A1, while the lower right corner will be H5.

The puzzle grid is laid out in this fashion:
A B C D E F G H
1 A1 B1 C1 D1 E1 F1 G1 H1
2 A2 B2 C2 D2 E2 F2 G2 H2
3 A3 B3 C3 D3 E3 F3 G3 H3
4 A4 B4 C4 D4 E4 F4 G4 H4
5 A5 B5 C5 D5 E5 F5 G5 H5

Upper left corner is A1, lower left corner is A5, upper right corner is H1, and lower right corner is H5.