Accessory case A-902 This neat aluminium box [some contents absent] together with the items below are part of Test tool set AN/USM-3A. A good description of the latter can be found here. All the rest of the equipment is pictured here. USA.
This is one of several items given to me by Deborah Waters, which belonged to her late father.
Internal view showing the 2 watt resistors.
Internal view showing the capacitors.