Quick and dirty teardowns - Two old Wheatstone Bridges

[intabits]

A couple of quick and dirty teardowns of two old Wheatstone bridges, picked up recently at a garage sale.

The first is a model WB4 from Victorian Measurement Laboratory (now defunct it seems) from circa 1959. A nice unit that might scrub up very nicely with some TLC. Unfortunately, it appears that the galvanometer is cactus, but further investigation is required to be sure.

It can also be used simply as a decade resistance box, and is reasonably accurate at about 0.1%.






Video:



The second is a "Portable Resistance Measurement Bridge" aka a "Post Office Box" (for testing telephone lines), possibly from around 1941. The resistance adjustment is performed by inserting pegs to short out fixed resistances. I'm not sure what is the best way to ensure good contact with the pegs or how best to clean the contact surfaces. Any ideas?







Video:



There is another, but with knobs missing and some disconnected internal wiring. Could be made into a good decade resistance box.
(no video for this one, maybe later if there's any interest)