Found at Reuse Center. Nut is stamped: DICK. From what I've read on the interwebs, Dick Brothers was a brass goods foundry in the early 20th century, located in Reading, PA. I believe this part is for connecting a wall-mounted faucet to 1/2" nipples that would extend through the wall. Please study the photos to be sure it is the right part for your application.
Thanks for looking.