One user noticed that each of his clothespins had a different number.
These numbers correspond to the molds used in industrial manufacturing. If a defect occurs in a batch of pliers, the manufacturer can quickly identify and replace the responsible mold.
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A strange device that was mounted near a door.

On some walls there is a small device with a hole and a miniature screen.
This is typically an alarm system installed near an outside door, for example, leading to the garden or swimming pool. It detects when the door is opened and triggers an audible alarm.
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A wooden ball covered with screws