What was the first product Hewlett-Packard sold after its 1939 founding?

The first product Hewlett-Packard sold after its 1939 founding was an audio oscillator.

Bill Hewlett designed the HP 200A, an electronic instrument that generated precise audio-frequency signals for testing sound equipment. Its relatively low price and practical design helped Hewlett-Packard establish itself as an instrumentation company rather than a consumer-electronics manufacturer.

Walt Disney Studios became an important early customer. Disney purchased eight oscillators for testing and calibrating the sound systems used with the film Fantasia, which was released in 1940. That order gave the young company valuable revenue and a high-profile customer soon after its launch.

The product is often called the HP 200A audio oscillator. It was not Hewlett-Packard’s later scientific calculator or printer business, both of which became famous decades afterward. The oscillator represents the company’s early focus on electronic measurement equipment.