The VGT128 argon filled thyratron is from the 1930s and was used in timebases for Radar. The fact that it is a UK Armed Forces badged GT1C is clear from the logo on the side.

The precision of construction gives the defined and reproducible operating characteristics. This valve not only has a high peak current but is designed for operation at up to 8,000 pulses per second.

The worlds first computer, Colossus, used these thyratrons as pulse generators. The operating speed of Colossus was 5,000 cycles per second.

The classic envelope is 42 mm in diameter, and excluding the B5 base pins, is 100 mm tall.

References: Datasheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type VGT128 was first introduced^¶ in 1937.

 
Pin Connections

B5	1	2	3	4	5
	a	g1	h	h	k

 
Absolute Maximum Operating Conditions^¶

Thyratron	Vh	Ah	Va	mAa
	4.0	1.35	500	1000

Thanks to Frank Philipse for supplying the above PDF datasheet