Dr. Bortini Wheatstone Bridge This was in need of attention, three of the internal resistors needed repair or replacement and the zero adjuster on the meter was ineffectual. Pavia, Italy, date unknown.
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
The variable resistance arm of the bridge totals 10000 ohms divided into four banks, each comprising four bifilar wire wound resistors on insulated brass tubes. They are all in the ratio 1:1:3:4 [thus enabling all values between 1 an 9 to be obtained]. A 1000 ohm high stability resistor has been connected across one of the open circuit ones, another has been repaired and the one missing from the ratio arm [near the meter] when I received the instrument has been replaced by two wire wound ones in series. The meter was removed and the zero adjuster was realigned so that it engaged with the meter movement. The unit has been tested and now works well.
How much is it worth? Instruments such as this are of little use today and not many people seem interested in them. Expect to pay £10-£15.