A chest full of jewelry and coins is in the room.
The chest lid is spring loaded, controlled by a pressure plate on the bottom of the chest. The edges of the chest lid conceal blades.
After the chest is opened the following can be found.
A DC 12 Intelligence (Investigation) check reveals that the lid seems to have some resistance to moving. This is caused by springs concealed in the hinges, which can be found with a DC 14 Wisdom (Perception) check.
A DC 14 Wisdom (Perception) check detects blades that run just under the lip of the chest lid.
A DC 16 Wisdom (Perception) check detects that the bottom of the chest seems loose.
The bottom of the lid is a pressure plate. When 100gp worth of weight is removed from the chest, the lid snaps shut. The target must make a DC 14 Dexterity saving throw or take 4d6 slashing damage and suffer from the poisoned condition until the damage dealt is fully healed.
The trap can be circumvented by simply adding weight before removing the contents.
It can be disabled by jamming the hinges, which requires a successful DC 14 Dexterity check with thieves’ tools.
If the hinges are removed or broken, or the lid is removed, the trap is activated.