Oomodo's bit about the cat gave me this idea:
You know about the buttered-feline perpetual-motion (BFPM) machine, right? If not:
-Buttered toast always lands butter-side down.
-Dropped cats always land on their feet.
-Ergo, if you tie a slice of buttered toast buttered-side-up to the back of a cat, then drop the cat upside-down, the cat will spin in place, balanced by two opposing forces.
Now, what you do is place two BFPMs on opposite sides of the tin, facing opposite directions. Tie the BFPMs to handy mounting points on the tin, with about a 36" length of stout hemp rope. Pick up the BFPMs, turn them over, and drop them (level III armor may be indicated here). Within seconds, the slack in the rope will be wound around the BFPMs, and the resulting torque will pop the tin right open.
You're welcome.
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"Taking a long view of history, we may say that
anyone who lays down his arms deserves whatever he gets."
--Jeff Cooper