The CV2213 is a miniature gas filled voltage reference with flying leads. It was designed for very low current use. The specification was issued by the UK General Post Office and the commercial prototype was the NT2 from Hivac.
This exhibit is still within the polythene package it was sealed within in 1970. For images of the reference itself see CV2213.
The reverse of the pack. The valve is within the corrugated card.
The package seen side on.
The thin glass tube envelope is 6 mm in diameter, and excluding the base wires is 21 mm tall.
Reference: Datasheet. Type CV2213 was first introduced in 1956.