The 12C1087-1 is a non-turn washer accessory designed for Grayhill rotary switches in Series 5000, 24, 42, 43, 44, 54, 71B, 53, and 59. This brass component with tin/zinc plating features an internal key that slides into the bushing keyway and a right-angle tab that locks into a predrilled hole on the back side of the mounting panel, preventing unwanted rotation. The washer has an outside diameter of approximately 0.625 inches (15.88 mm) and a thickness of 0.060 inches (1.52 mm), with a bushing diameter of 0.376 inches (9.55 mm). This accessory is commonly used in applications requiring secure panel mounting of rotary switches, ensuring stable operation and preventing accidental rotation during equipment use.