Sloan 0323210 Chrome 3/4" X 10" Vacuum Breaker V-500-AA & Spud Nut & NPT Adapter.

The adapter of top screws on top of the vacuum breaker and allows you to attach a 1/2 female adapter of your liking as a water supply. mostly this would be used with a spring-loaded valve that you open and then automatically shuts when you let it go to flush the urnial.

Missing cardboard Slide Washer for vacuum breaker