Find this and other symbols in Hornung's Handbook of Designs and Devices, first published in 1932. https://en.wikipedia.org/wiki/Clarence_P._Hornung https://en

Find this and other symbols in Hornung's Handbook of Designs and Devices, first published in 1932. https://en.wikipedia.org/wiki/Clarence_P._Hornung https://en.wikipedia.org/wiki/Clarence_P._Hornung http://www.amazon.co.jp/Handbook-Designs-Devices-Pictorial-Archive/dp/0486201252 http://www.amazon.co.jp/Handbook-Designs-Devices-Pictorial-A...