This is a Lock & Cancel Valve used in many pneumatically controlled instruments. It turns pneumatics or vacuum cutouts on and off. For example a Glockenspiel, Accordion or Xylophone. The opening of the 5/32" elbow on top of the valve allows the vacuum to flow threw the 1/4" nipple at the side. Opening of the other 5/32" elbow will stop the flow of vacuum. These units are built with adjustable Wurlitzer type valves.