1925 - 1930
The Duophone label was named after a record player made by the Duophone Syndicate Ltd., of 63 Queen Victoria Street, London.
In October 1925, it released its first The Duophone pressing.
In November 1926, the company released "the revolution of the decade" which were ‘unbreakable', and sported the same general design but were now gold on black. The problem was that whereas the records themselves were very sturdy and would not break on droppping, the grooves were fragile and could not take much more than a fibre needle.
In August 1928, the Duophone and Unbreakable Record Company Ltd., as it was now called, gained control of British Brunswick, and released a new label that no longer showed the duophone recording head on the label.
The D-4001 upward series thus featured many American dance bands that were contracted to Brunwick-Balke-Collender. It is important to note that these later Duophone pressings included the Brunswick catalog numbers, which gave more artist detail.
In 1929 the final series were released, F-2001 upwards; these are significant in that they did not include any Amercian artists, but featured one of Britain's finest arrangers and bandleaders, Lew Stone.
The end of 1930 was also the end of Duophone.
(Thanks to MGTHOMAS)