This is a beautiful valve. The 13E1 is a beam tetrode designed for DC control applications. The ratings are absolute maxima and based on its intended use as a series pass devices for generating stabilised HT rails.

Inside the anode can be seen two separate cathode and grid structures, both connected in parallel within the envelope.

The picture shows both the valves, and especially the golden control grid wire.

In this photograph of the bottom of the envelope, the insulated heater wires can clearly be seen. Also visible are the glass pips that the pins pass through.

The wide glass tube envelope is 60 mm in diameter and, excluding the B7A base pins, is 117 mm tall.

References: Datasheet & ¹⁰⁴⁰. Type 13E1 was first introduced^¶ in 1960.

 
Pin Connections

B7A	1	2	3	4	5	6	7
	h	hct	g1	k	g2	a	h

 
Absolute Maximum Operating Conditions^¶

Beam Tetrode	Vh	Ah	Va	Vs	mAa	gm	Pdiss
	13.0	2.6	800	300	300	35.0	90W

Thanks to Frank Philipse for supplying the above PDF datasheet

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