Nudge
... and any item that was placed in the charity chest would be marked so it could not be resold.
That sounds good but it may require some programming resources.
To reduce the amount of work in implementing the "item cannot be resold" attribute could new items that are deposited just loose enough HP so that vendors will not resell them?
"The %itemname% rattled and clanged as it slid down the deposit chute and landed amongst the swords and maces at the bottom of the chute, it may be slightly more secondhand than it was a moment ago"