[Milsurplus] Trio Labs DC meter

[John Watkins via Milsurplus]

Just dug out a Trio Labs (Seafort NY) DC VTVM, small 6X4X4 inch box, 115 400 Hz power.  looks like it is from an aircraft such as AWACS, etc.  May be part of AB test set?  Model # is SJ487.  It is center reading and goes + or -.  Has 2 5751s in it and solid state PS.  .01 to 300 volts DC.

Anyone have any data or a schematic on it?

Thanks,

John  WD5ENU