I've been involved with oscillators for various requirements over the years, but nothing remotely connected to servicing FM tuners. Could you explain why this task benefits from a low distortion waveform? My impression (perhaps erroneous) regarding FM tuner set up was that alignment of the IF amps was fairly critical, and that a good instrument for doing that job is a wobbulator? I do have a 10.7MHz wobbulator, bought some years ago from a friend, but I've never actually used it.
In terms of FM tuners, I still have a ~35 year old NAD 7020 in daily use, but I'm pleased to say that I've never had to do any service work on that
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Incidentally, are you familiar with this UK forum
https://www.vintage-radio.net/forum/index.php. There are some very knowledgeable devotees of FM radio on there; DAB is a swear word.