Thank you for this comprehensive information Guenther.
I have always wondered why a 455kHz IF was chosen, why this frequency ?
And I have also seen circuits using a different frequency.
Important to know when you would like to align a radio.
Also interesting to know that in a combination of FM and AM, the IF stages share the same IF transistor (this can also be seen in your last picture).
Ive been repairing a lot of these circuits at my former job and aligning those stages.
Sometimes the small capacitors inside the IF coils tended to drift.
This was primarily in TVs and I used an oscilloscope to find the resonant peak.
If these coils were out of tune, the TV station was out of tune and the auto search function didn’t perform well.