Gauge adapter and charging valve. Charge valve is a schrader like a tire fill valve but has no guts. One of the nuts moves the stem and seals it. Accumulator tag came with it and shows it came off Northwest Airlines tail number N1161US 5/06 when it was scrapped. I googled that aircraft and it set a speed record Feb. 96 from Washington DC to Amsterdam. you never know what google is going to come up with!
Sub-class : C-1 (Landplanes)
Speed over a Commercial Air Route : 993.13 km/h
Date of flight: 17/02/1996
Pilot: David J. ROTH (USA)
Course/place: Washington, DC (USA) - Amsterdam (The Netherlands)
McDonnell Douglas DC-10-40
I'm holding the gauge adapter made from 3/4 round CRS. The external threads are kind of a reverse O-Ring boss style fitting. Threads are 7/16 X 20 and the angle of the O-Ring seat is 11 degrees. The other end is tapped 1/4 NPT for the gauge. Getting pipe thread to seal at these pressures was kind of a tussle. Ended up using 320 grit lapping compound and a pipe nipple to lap them in. The original gauge was no good.