The GN-4P is a cold cathode numerical indicator tube with a clear glass envelope. The digit current is 2 mA.
The construction is of a common anode, and a series of shaped cathodes. Each cathode being in the shape of a number from 0 to 9. This were stacked on support rods and each cathode was brought out to its own pin. Energised by around 180 volts a open collector based TTL chip would interface between the digital circuitry and the display. As each cathode was connected to ground the glow of the neon gas filling would form found the cathode and through the end window the shape of the numeral would be visible.
The STC logo.
The stack of shaped cathodes with ceramic spacers between.
The stack of shaped cathodes and the open square mesh anode.
The end window envelope is 29 mm in diameter, and excluding the B13B base pins is 26 mm tall.