国立アメリカ歴史博物館のインスタグラム(amhistorymuseum) - 4月11日 05時11分

Today in 1838: Inventor Frank Baldwin is born. This is a production model of his pinwheel calculating machine from 1875.
On a pinwheel calculating machine, digits are represented by retractable pins. Setting the machine consists of moving levers that release an appropriate number of pins, which are engaged when the crank rotates.
Not currently on display.
#Math #TodayInHistory

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