Weston centre zero microammeter 75/0/75 microamps full scale deflection. The meter is brought into circuit via a push button between the terminals, this is depressed when the lid of the box is closed. The meter is working. Date unknown. Weston Electrical Instrument Company, Newark New Jersey USA.
This is one of many instruments collected by Jack Davidson C Eng FIEE which I have been given by Dr Graham Winbolt
Front panel of the instrument
Edward Weston [1850-1936] founded the Weston Electrical Instrument Company and held 334 patents.