The KTZ63 RF amplifier pentode, equivalent to a 6J7G was also noted as a low noise audio pre-amplifier.

The classic envelope is 36 mm in diameter and, excluding the IO base pins, is 93 mm tall.

References: Datasheet & ¹⁰⁴³. Type KTZ63 was first introduced^¶ in 1937.

 
Pin Connections

IO	1	2	3	4	5	6	7	8	tc
	m	h	a	g2	g3	-	h	k	g1

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.3	250	100	-2	1.0	0.25	1.5M	1.23

Thanks to Frank Philipse for supplying the above PDF datasheet