Many unusual display tubes were manufactured by the Soviets during the Cold War, but this strange device shows that even the humble pilot light is not beyond replacement with a complex electron tube. This display contains a red phosphor target, control grid, filaments, and all the other elements of a typical VFD display, but instead of displaying numbers or symbols the tube is dominated by a single square target that fills nearly the entire face of the envelope. We have no idea why such a device would be created, but since the display contains a control grid, it is possible it was intended for high-speed indication applications where the latency of an incandescent light bulb would be unacceptable.
The exact manufacturer of this display is a bit of a mystery. The device appears mechanically identical to a Russian-made ILD1 single pixel indicator, but the ILD1 uses a green phosphor, not the red seen here. Exhaustive research of all available Russian databooks has turned up no known red phosphor single pixel display in this package, which suggests that this may be a special order device or some sort of prototype.
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