These 1950's tubes function both as counters and displays. Tube has 30 cathodes arranged around a central anode disc. Each cathode is connected to one of three external pins, forming ten electrode groups. Applying three sequentially phased pulses to these pins makes the glow discharge jump from one electrode to the next. An external phase-shift network is used to provide the sequencing, resulting in a counter that advances the glow by three electrodes for every single input pulse. These tubes were often used in geiger and frequency counter applications, and as prescalers for a mechanical counter, count rates up to 1Khz being possible. Dekatron is bidirectional (is able to count clockwise and vice versa).
There are available dekatrons with black and brown bases.