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The SP2D is an RF pentode from Tungsram. It is a battery valve with a two volt filament that consumes 100 mA.

A B4 based version was released in 1938 with the B7 based version following the next year.

The control grid connects to the top cap. Within the glass the filament tension springs can be seen.

The B7 base pins.

Thanks to Mark Mallison for sending the images.

The classic envelope is  mm in diameter, and excluding the B7 base pins is  mm tall.

Reference: ¹⁰⁴³. Type SP2D was first introduced in 1938. See also 1938 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶