The ZM1022 is a numerical indicator tube with a clear glass envelope. The ZM1020 has a red filter applied. These appear to be identical to the STC GN-4A and GN-4 respectively.
The stack of shaped cathodes is separated by ceramic insulators. The fine wires connecting the cathodes to the base pins can be seen.
The stack of cathodes: each one is in the shape of the numeral to be displayed. When energised the glow surrounds the illuminated cathode.
The thin glass tube envelope is 28 mm in diameter, and excluding the B13B base pins is 25 mm tall.
