An older wooden cased ohmmeter by Clare Instruments, Worthing.
This device is used to measure resistance, and has two scales - 2 ohms and 0.2 ohms.
Intended for continuity measurements of steel conduit and protective bonding conductors, which should have a very low resistance and if a fault occurs will need to carry a substantial current.
Unlike modern battery operated meters which typically apply 200mA DC, this applies approximately 30 amps AC with the leads shorted.
Current drops to about 15 amps with a 1 ohm test resistance.
This video shows the device in use, and a measurement of the test current is taken.
The front panel is then removed for a look at the internal components.
A low resolution version shown here for viewing on screen.
Download high resolution version for printing: TIFF, 651kB