The VP41 is a variable-mu RF amplifier pentode from Mazda. Although released in 1938 Mazda were still advertising it in 1948 when the world was moving to smaller all glass valves.

The classic envelope is 32 mm in diameter and, excluding the MO base pins, is 90 mm tall.

References: Datasheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type VP41 was first introduced^¶ in 1938.

 
Pin Connections

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

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	4.0	0.65	250	200	-2.7	7.7	2.0	1.3M	2.0

Thanks to Frank Philipse for supplying the above PDF datasheet