ANSWERS: 1
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The hand warmer was invented in 1923 by Japanese inventor Niichi Matoba. His hand warmer became known as the Hakukin-kairo, or butterfly personal heater. Japan's MyCoal Corporation invented the disposable hand warmer in 1981, which is now sold by its American affiliate company Mycoal USA.
Source:
Mathaba.net: Pocket Warmer History
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