The GC10B/1 is a cold cathode counting and display tube. The orange display comes from the neon gas inside. This tube has a central common anode. The discharge would cause one of the cathodes to glow and its position would indicate a number. To advance the display the inter cathode pin electrode(s) would be energised and so would the next cathode. The discharge would walk to the next cathode using the pin(s) as a guide.

The end window envelope is 27 mm in diameter and, excluding the IO base pins, is 84 mm tall.

References: Datasheet

 
Absolute Maximum Operating Conditions^¶

Indicator	Va	mAa
	300	0.5

Thanks to Frank Philipse for supplying the above PDF datasheet