Amplifier component identification

This is a component inside a measuring device. This is a pre-amplifier. Does anyone know the function of the coil on the top (looks like a small transformer)? What is the functionality of that? How to identify the specification of that coil ?

The second attachment shows how the coil windings are connected. Why 1' and 2 are connected

Gonna be hard to identify working without schematic. If you don't have it, you can draw one by tracing the PCB. Component values are mostly easy to find through colour codling and markings.

To determine the value if it's not written on it: desolder the part and measure it's value.

dayDreamer1013:
The second attachment shows how the coil windings are connected. Why 1' and 2 are connected

Bit short on attachments however. :astonished:

There were attachments - apparently removed since...