The instrument itself contains a Weston standard cell (1.01 volts) manufactured by Tinsley in 1961. Unfortunately the cell voltage is now only 43 millivolts! The other problem was that the taut wire of the galvanometer suspension was broken. I have soldered the finest wire I could find to enable it to more or less function.
Here are the large 1.5 volt cells which power the two parts of the circuit, the covers on the left have expanding rubber seals to keep them in place.
This is a similar one recently auctioned on eBay
