Electron Company Limited was registered in May 1923 as a valve maker. The business operated with a factory at Acton Lane in Harlesden North London. Production commenced in 1924 with a dull emitter type and employed the trade name Six Sixty.
In 1926 the company signed an exclusive ten year agreement with Mullard to sell Mullard valves as the Six Sixty brand and closed its own manufacture. In 1928 Mullard purchased all of the shares in the Electron Company and renamed the business Six Sixty Radio Co. Ltd.
The Six Sixty Radio company was used as a retail brand for second quality valves. These were Azide PM valves and the process produced considerable numbers that failed the strict quality control process but still worked. Philips or Mullard sold the full specification devices but as valves were of great expence in the 1920s the seconds brand had good sales.
In 1935 Mullard again made a ten year agreement with Six Sixty to supply it with valves. With this agreement in place the Philips/Mullard company sold Six Sixty to Ever Ready Limited.
The picture above is the reverse of a playing card. The design clearly reflects the art deco movement of the time.