Alternative front seats for 123.
 

This link is from the craigslist thread. Notice the front seats. I think they look better than the OE seats. Anyone recognize them? Anyone tried using them?

1981 Mercedes 300 Turbo Diesel Wagon (Reduced)

Those look like Audi Ur-S4/6 or BMW M seats

Best guess those are Recaros, further guess probably out of a high-end 3-Series or 5-Series BMW, circa 1980s (though you could buy them from Recaro, of course, these would be low to mid end by Recaro price standards). Many of BMWs came with either black or cream leather Recaros, with the movable front thigh bolster. VW had a similar seat in some A2 Jetta GLXs but I don't recall the leather looked like that.

I had a set in my Volvo 164e. Whether they are a good idea depends on your taste. They are firm, sports-oriented seats. They work better if you are narrow of beam (I am not, so the side bolsters dug in a bit after an hour). You will notice the side bolster a bit, versus a normal seat, when you get in and out.

They are semi-orthopedic in design with an adjustable back support and at least for me, my sore back loved them.

The original BMW base had tilt adjustment, which I lost when I installed them with the Volvo adapter.

In the day Recaro sold adaptors to bolt into many cars. It wouldn't be hard to fabricate something to bolt them up to a w123 base, I would imagine.