An original pair of WW-II American Army Air Force Offered for your consideration is a WWII Bomber Pilot Headset Model HS-33.   The HS-33 Headset is a nominal 600 ohm (“low impedance”) unit utilizing receivers marked:   RECEIVER ANB-H-1 Western Electric Made in USA D173120 Since both the older high impedance (HS-18) and newer low impedance (HS-33)  headsets were in use during the same time period, the HS-33 plug, designated PL-354, was color-coded bright red.  The short interface cable is intended for use with an extension cable which permits a pilot to unplug and move about while the extension cable remains plugged into the aircraft.   FYI -- the extension cable (not furnished) may be identified by the marking ”N.A.F. No. 215284-2” on the headset mating connector and “N.A.F. No. 1136-1” on the aircraft mating connector.   (Note that the HS-33 headset works very well with WWII bomber HF receivers such as the BC-348 which has nominal 600 ohm audio output jacks.)     This headset has been tested and is working; however, the spring assembly on one side has broken as can be seen in the photographs.  A quick spot weld would fix it, but it’s probably a parts unit.  The owner apparently continued to use the headset, resulting in fraying of the harness and intermittent operation.  The unit is therefore listed as “Parts or Not Working”.  Both receivers work well and are very easily switched between headbands.