Looks like the aftermarket brass jam nut included in Borg-Warner brand rebuild kits. That means the valve was probably a Borg-Warner version item also.
My experience with the Borg-Warner kits is all bad. I never used one but I repaired Shelby and Boss Mustang carburetors somebody else put their kits in. The needle and seat threads were normally a little smaller than required to have a good fit. Users sometimes had slow fuel leaks at the jam nut and sometimes in efforts to stop the leakage somebody kept tightening the nut and ended up ripping some to a lot of the threads out of the fuel bowl.