Lucy,
I think that you have to check again, as ASTM B 16 standard (2001) regards non-ferrous alloys and in particular "identifies requirements for free-cutting brass rod, wire, bar and shapes of any defined cross section produced from Copper Alloy UNS No. C36000 appropriate for high-speed screw machining applications and moderate thread rolling".
May be the reference standard the Customer requires is ASME B16.34?
This is almost "the Bible" of Valve Manufacturing, as it "covers new valve construction and pressure-temperature ratings, dimensions, tolerances, materials, non-destructive examination requirements, testing, and marking for forged, cast and fabricated flanged, threaded and welding end, and wafer or flangeless valves of steel, nickel-base alloys and other alloys. Also gives detailed diagrams, tables and annexes".
Bye, 'NGL