Suppose you have access to one of those boxes, whether legitimately or just because it's open at the top, and you see a particular quarter you'd like to have. Is it acceptable to swap it out for a quarter of your own?
Sounds obviously fine, right? For instance, if you collect state quarters and you're only missing Maine, and you see one in the box, it doesn't hurt anyone to swap it for that extra Florida quarter you have on you. (And have grown to resent a little more every day for not being Maine. Poor Florida.)
But what if it's not just any quarter? What if it's that rare 2004 Wisconsin state quarter with an extra leaf that's worth $300 to collectors? Can you make the swap then?
You can probably assume the donator didn't know he was putting something that valuable in the box. (If he did, why would he just count on somebody at the charity recognizing its value?) He only intended to give a quarter. The charity will probably only USE it as a quarter. You may be the only person at any point in the chain who notices its value.
And yet... that quarter IS in the box. It's the property of that charity now. If you swap it out, a total of $299.75 has gone from the charity's possession to yours. It just won't know that -- because it didn't know it had that amount in the first place, and will in fact NEVER know either way.
So, in this second case, is the swap acceptable or not? If not, does that apply even to a quarter worth 25.0001 cents? If so, does that apply to a quarter worth a million dollars? And what makes this feel so different from the first case? Almost all the variables are the same -- the coin is worth more not to the donator or the donatee, but only to you. Why is it important that in the second case, other people who aren't even involved will agree that it's worth more?
(Please note: This is completely hypothetical. I have no access to a box like this -- even the one I saw today was closed -- and I also have no idea what coins are valuable. I had to google an example.)