Safecracker

Relevance:
Hardly anything *is* relevant.

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Real-time:
*) entire game -- overall 12 hour time limit, probably sufficient for most,
   but save/restore makes it irrelevant
*) piano -- (perceptual) a tone match
*) hand dryer -- plenty of time to put the key into the lock before the machine
   shuts off, and you are free to repeat

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Reasonability:
*) venus de milo -- I didn't notice her picture anywhere, but I wasn't looking
   until after I found the puzzle. If you aren't familiar with the work, this
   would devolve into a tedious trial and error combination lock.

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Difficulty:
Neither of these are original, but if you haven't seen them before they could
require a bit of head-scratching:
*) flower safe -- A standard variation on the "assemble N base vectors to get
   to your destination".
*) key weighing machine -- Two tests to find the unique object.