The Schwarz chest plate gun was a prototype clandestine 8 barrel volley gun installed in a body armour vest. It was designed to be worn under a jacket and fired when the user raises hands up, actuates firing by pulling strings that fire the weapon. The weapon was designed by the Chicagoan Samuel Schwarz in 1929.
References[]
"Vest Machine Gun" Pours Bullets into Bandits. Popular Science Monthly, March 1929, Page 69.