[Daren]

Below is text from the Hohner website. It also says the 1958 melodica was the soprano button:

HOHNER –
The original inventor of the Melodica
More than 50 years ago HOHNER invented the Melodica. This new musical instrument was intended to ful ll the special demands of early music education.

In November 1958 a German language brochure presented this creation for the rst time – the Soprano Melodica with its original stump keys. In 1959 the Melodica was successfully introduced internationally and soon established itself as one of the world‘s most popular beginner ́s instrument.

Very soon professional musicians also discovered the charm of Melodica ́s unique sound. This led to the release of the Piano Melodica in 1961. In 1975 it was estimated that one million people played the Melodica in Germany alone.
Today the Melodica is experiencing a renaissance. It requires no socket, so you can take it with you and play it anywhere. The Melodica has a unique, natural sound which is held in high regard by traditional pop and jazz musicians as well as young alternative bands and experimental artists. More than 55 years after its introduction, the melodica is still the ideal companion for beginners and professional alike who cherish a full, natural sound as well as a wide range of expression, playing comfort, and independency.