The calibre seems me to be 12mm blank.
Diameter of the chamber: 12,10mm
Length of the chamber: 17mm
Diameter of the site of the base: 15, 20mm
Height of this one: 15mm
Here the ancestor of our alarms theft protection device: this object is a warning signal of effraction; charged of a blank cartridge, its own weight involves the percussion in the event of fall since a certain height (1m or more).
The higher hole made it possible to suspend it in not very stable position, inside the door to protect… a malevolent jolt took down some, the detonation alerting the owner - and the vicinity! …
The intruder thus discovered was supposed to give up as fast as possible, the more so as it had bad conscience and was believed taken for target.
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