This is the Dual Power Supply for ODEC Outdoor Ellipsoidal (120V).
The ellipsoidal itself is a zoom-focus, variable-angle fixture capable of projecting patterns or images on a surface. The power supply which fits into the back of the fixture, enables projection of gobos by powering such accessories as the Internal Indexing Rotator (99-TS-5278) and the Internal Non-Indexing Rotator (99-TS-5222).