It is a jewel-encrusted black box, seemingly made out of a dark exotic wood, a mere few inches across, so it can be held rather comfortably in one hand, although it certainly feels a little bit heavy for its size.
At first glance, it might even seem a bit cheap. However, there is something remarkable about this box: the top panel can be opened and items placed inside; Once it is closed again a turning-gear sound is heard and the top panel locks and becomes inaccessible; After about 7 hours, the top lock reopens and a previously invisible lower panel also pops open, with whatever items were placed in the top panel perfectly duplicated in the bottom panel, as far as you can tell.
You gained control of the box seemingly by accident. Someone you met briefly seems to have left it behind. Come to think of it, you don't remember the night very clearly. You do recall her name was Rynn and she had an easy laugh and eyes so green you could almost swear they had an inner glow of their own. Much of the rest was a blur. A wonderful blur.
What is the best way to use the box? You've considered placing money, diamonds, or LSD inside. However, you're just a regular person living somewhere in the Western world. You wouldn't even know where to buy LSD from if you wanted to. You're not a drug dealer or a diamond merchant, and you don't want drug lords, or worse, the government, or for that matter anyone else taking it away. It's not (just) greed: you're still holding on to the hope that Rynn might return one day for her box.
*EDIT: In response to the perhaps predictable cries for clarification, I refuse to engage in a definition of what "good" is (as I see it, an exercise best left for philosophy.stackexchange.com) but rather reaffirm the initial goals. The goal is to use the box, while incurring only a trivially small chance of getting discovered, in a way that would seem rational and reasonable to a moderately socially-apt, moderately ethical, moderately-well educated and moderately financially savvy Westerner.
EDIT 2: Ok, What is an efficient way to use the box to get obscenely rich and/or do the most helpful deeds towards bettering the state of mankind (according to your best judgement) while ensuring that your use of the box remains undetected and the box stays in your possession?