Maker's Name: 
18 × 12 × 6.3 cm

Part of a wireless telegraphy transmitter from the first decade of the twentieth century. Four spark gaps are in series, one adjustable 0-2 mm, three adjustable 0-3 mm.

Probably designed for use in the range 5-15 kV. The shafts are steel tipped with tungsten, naturally cooled by coaxial copper discs.

The aim of spark quenching is to have only a few cycles of RF generated but with minimum decrement. The RF signal then has maximum energy over minimum bandwidth.

Methods used for quenching included cooling the gap by radiation, convection, and conduction, blowing air across the gap to cool the spark and blow it sideways, using an AC magnetic field to cause the spark to spread and cool down quickly.

Here the spark is caused to spread using disc gaps where the gap increases with radius. The spark is meant to expand like a circular 'Jacob's ladder' discharge and dissipate.