Jezail

I had remained indoors all day, for the weather had taken a sudden turn to rain, with high autumnal winds, and the Jezail bullet which I had brought back in one of my limbs as a relic of my Afghan campaign throbbed with dull persistence.
(Adventure X, pg. 131)

In the novel, this is the weapon that would have woulded Dr. Watson during his military service in Afghanistan.

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