Cartridge box
The cartridge box was a box to carry cartridges. It was worn on the soldier's right hip, on a belt in front of the soldier's belly ("ventral cartridge box", "gargoussier"), or on a shoulder belt.
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Wikipedia
The cartridge box was a box to carry cartridges. It was worn on the soldier's right hip, on a belt in front of the soldier's belly ("ventral cartridge box", "gargoussier"), or on a shoulder belt.