This is a British crystal set made in the US. It was introduced in 1923. The GPO registration number is 4043. It has a high-low switch. The high refers to the High-power, long-wave station at Chemsford. The medium wave stations were also referred to as low-power. So, it is a long-wave/medium wave switch. It is the only one of these high-low switch Mepoons I have ever seen.