These units were used for Multi-Image slide presentations to buffer the Modulated Pulses being sent to the slide projector controllers.
No other information is available regarding this unit. Made by Audio Visual Labs.
This is a 1.16x multiplier for Navitar 35mm slide projection lenses. It fits between the focus tube and the rear element, turning a 7" lens into 8.12", 9" to 10.44", etc. This piece has a small crack in the rear element.