The 959 is an acorn pentode designed for battery use. We know of no commercial use for high frequency acorn valves and think that they may have been designed for military use. Possibly in portable VHF radio equipment, but this remains at present just speculation.

The acorn envelope is 14 mm in diameter and, excluding from tip to tip is 44 mm tall.

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	1.25	0.05	145	67.5	-3.0	1.7	0.4	0.8M	0.6

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 12 June 2007 {find valves by name}