You have a Microcassette, Mini-Cassette, Picocassette or Steno-Cassette
These four types of cassettes are smaller than Compact Cassettes. You often find them in dictaphones.
The person who bought a dictaphone or an answering machine in 1967 possibly needed Mini-Cassettes. These cassettes – developed by the Dutch company Philips – were perfect for these kinds of applications, because of their compact dimensions.
Mini-Cassettes were about half to a third smaller than Compact Cassettes. That reduction is reflected in the recording time. You could record audio for a maximum of 30 minutes with a Mini-Cassette. That was enough for most interviews and telephone messages, though.
Olympus introduced the Microcassette in 1969. The idea behind it was simple: a magnetic tape with the same width as the Compact Cassette, but in a smaller casing. Do not be fooled by the compact dimensions. The cassettes had a playing time of 45 minutes because the tape was thinner and a different recording speed was used.
Microcassettes were mostly used as voice recorders, more specifically in Dictaphones and answering machines. Some people recorded their favourite music on it. It was even used for data storage.
The Steno-Cassette was developed by Grundig in 1971 to use in Dictaphones. You can recognise it by the inscription ‘Steno-Cassette’ or by the typical measuring bar on top. This cassette can contain up to 30 minutes of audio.
The Picocassette (also known as Dictasette) is the smallest of all audiocassettes. This carrier was developed for voice recordings by Dictaphone in association with JVC. There was room for up to 60 minutes of audio segments. After the launch in 1985, the cassettes stayed in use for some years.