What fitting is this?

Test the Edelmann fitting first before making your brake line. I bought one for my later model two-bolt aluminum master cylinder because it has that same weird 9/16-20 thread and the Edelmann fitting was too short. There wasn't enough thread on it to firmly seat the double flare on the brake line to the seat in the MC. I ended up going to the pick-n-pull for the proper fitting.