The Turn Of The Century Electrotherapy
Micrometer Spark Gap Power Supply
Pancake Coil powered by cigar-box tank circuit
Box contains 1650V 10mA transformer and .0315 mfd condenser @ 7kV. [ (7) .22 mfd 1kV condensers in series]
Note the position of the conical adjustment - Gap is open 1/16".
As the cone is pushed or pulled the gap is adjusted - a 3" portion of the cone adjusts the gap by a maximum of 1/16".
Hints of what's inside...