Serial No. W 7650
Sangamo Weston Single phase Watt meter 0-500 Watts FSD housed in a broken Bakelite case with calibration certificate in lid. Now working. Date 1951. Enfield, London.UK.
This is one of many instruments collected by Bob Evans which I was given by his daughter Alice Kirby in 2015.
Bakelite case with later carrying handle and repaired crack
Interior view of the resistor banks note that each bank has a bobbin resistor in series with the switch connection.
Calibration certificate dated 1951 is in the removable lid.
Edward Weston [1850-1936] founded the Weston Electrical Instrument Company and held 334 patents. You will find information about Sangamo in this link as well.