This was driving me cracked. I brought it up in another thread but without the right pictures I couldn't explain myself. Anyway, I found them:
WarWagon's Time Bomb:
A Cannon Yellow Time Bomb:
The Cannon Red has a different dot pattern than the Cannon Yellow (the former is arrayed as though around triangles, the latter around squares).
The question is, are all Cannon Reds the same? Are all Cannon Yellows the same? When did the variation occur? Does anybody really care?
(BTW, lovely Time Bomb Mike)