India, Nov. 6 -- Fifteen years ago, Arambam Angamba Singh, then a young Manipuri civil engineer aged 33, made a difficult decision. On his desk at work were project documents for a building whose technical aspects he was supposed to supervise. Back home, in a drawer, was a gift from a friend - a World War 2-era Japanese light machine gun used in the Battle of Imphal-Kohima. The friend had found it while on a trek not far from their neighbourhood.

The documents on his desk were Singh's job; but he couldn't shake the feeling that in the rusty gun lay a future. He stayed at his desk that day, and for eight years after that.

Finally, in 2013, he quit the job and gave his life, as it were, to the gun. He became a self- taught researcher of m...