AVO 2 panel Valve tester overload assembly

[wave solder]

I've had and AVO 2 panel valve tester and used it for many years with no problems but the one I have got has had some missing parts ever since I have had it.
There is a tag strip with wires that go down to three contacts underneath the meter assembly.
If there is an overload a wire heats up and clamps part of the moving part of the meter against one of the three contacts.

Does anyone know what originally connected to the tag strip where the four wires are cropped in attached photo?

Thanks in advance.