Squareback vs round back alternator?

In the service manual:
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bad wire connection on the starter solenoid, it went loose my checking:

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The starter and ignition shows some very small resistance fluctuation while wiggling the key in the IGN1 and IGN2 position. Would like to replace but couldn't find so far the right one.
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I don't know how popular rockauto.com is in the US, but here people use it a lot for US cars.
They show only this starter / ignition switch:
There's an additional GRD contact. May it work the same way if I don't connect GRD or do we have the worng installed in the car!?
Maybe this gives also a hint to whether the field strengths is controlled by switching the positive feed, or by the negative connection ...?
#Ignition switch.PNG

The black wire is the one that goes from the starter switch IGN2 to the relay mentioned above, it's just connected "professionaly" to the wire:

The missing ignition ballast resistor should be connected in the engine area at this wire and the going to positive connection on the ign coil..

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Ah, I forget to say: Thank you all for welcoming me here and your support.
Christian