For your consideration is this very interesting Thomas Electroscope System B gold and silver detector.
This unit is complete with instructions and other paperwork.
This is powered by a single 9-volt battery (not included).
This powers on and appeared to track my gold ring which had been set on a table. There is a learning curve to using this instrument, though once mastered it is said to be very accurate.
This measures about 26″ in length with the antenna fully extended.
Please see the photos for more detail.