I couldn't remember it either, so you didn't see it.
Think HP came up with it, their first product. Before that most/all audio oscs were the beat-freq type.
I think those were in a contest with Swan to see which drifted the most.
TOM K8ERV Montrose Colo
Of the many projects they worked on, their very first financially successful product was a precision audio oscillator, the Model HP200A. Their innovation was the use of a small incandescent light bulb (known as a "pilot light") as a temperature dependent resistor in a critical portion of the circuit, the negative feedback loop which stabilized the amplitude of the output sinusoidal waveform. This allowed them to sell the Model 200A for $54.40 when competitors were selling less stable oscillators for over $200. The Model 200 series of generators continued until at least 1972 as the 200AB, still tube-based but improved in design through the years.
One of the company's earliest customers was Walt Disney Productions, which bought eight Model 200B oscillators (at $71.50 each) for use in certifying the Fantasoundsurround sound systems installed in theaters for the movie Fantasia.
Yep, from Wikipedia
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