Query: Who released 7" microgrooved records in the 1950s?
Context: This was done by the label mainly to take advantage of the wider audio frequency response that faster speeds like 78 rpm can provide for vinyl microgroove records, hence the label's name (obviously catering to the audiophiles of the 1950s "hi-fi" era, when stereo gear could provide a much wider range of audio than before). Also in the late 1950s, Bell Records released a few budget-priced 7" microgrooved records at 78 rpm.