Pye 7556

Described as a "thermocouple test set", this instrument is really another millivolt potentiometer and is not dissimilar to other instruments of its era, including the Cambridge offerings (W G Pye & Co was formed by an ex-Cambridge Instruments employee).

This one has all the usual functions associated with this style of potentiometer. Additionally, it can be configured into a Wheatstone bridge thus enabling resistance measurements to be performed, albeit over a limited range.