Do not know nothing about harps, I was in my storage building and saw 2 harps one was for a double lamp shade cast iron and the other one was a lot lighter if I had a picture I would go this weekend and look, Chuck...
Dont have a photo but is a chicken pulley bone shape with base to fit a standard post/pipe and a round bracket at top to hold the porcelain bonnet and the hanging socket from the top. Made of light alloy material, cast and hollow to run wiring through. thank you Larry