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Opening them without a specialized tool often required brute force. People used knives, chisels, hammers, or even bayonets to pierce the metal lids, making the process cumbersome, time-consuming, and dangerous.
While effective for its intended purpose, it was not particularly user-friendly for civilians, requiring both strength and dexterity.
Its design was so robust that it was occasionally compared to small weapons, a comparison not entirely unwarranted given its construction and potential to cause injury if mishandled.