That looks to be a Nathan lifting injector, which helps put water into the boiler. For drawings, you may have luck with live steam Facebook groups. There is a guy that has the page “Eccentric Engineer” who has done fantastic work, and may have a good reference library he’d be willing to share.
Edit: Upon looking at my copy of the 1941 Locomotive Cyclopedia, I’d say it’s a Nathan Simplex Type-R lifting injector. It looks like the pipe that extends from the top of it to the cab manifold that supplies steam is gone, along with the water delivery pipe that comes out on the right side of it.
