The GN4 nixie tubes range are numerical indicator tubes. The image is formed by the glow of the ionised gas around one of the shaped cathodes. This exhibit is labeled as the American ITT but Made in England. STC is the UK company.
GN4 has a red filter and the GN4-A has a clear glass envelope.
The ceramic insulators separate the thin shaped cathodes.
Face on reveals the stack of cathodes, each in the shape of a numeral.
The B13B base is 28 mm in diameter and 9 mm thick.
The base is designed for PCB mounting.
The thin glass tube envelope is 28 mm in diameter, and excluding the B13B base pins is 27 mm tall.
