The K frame was the 547. No moon clips needed, as it had these springy extractor fingers.
There was the J-frame 940 also, but I imagne you are referring to the 547. The 940 used moon clips.
I think there was a thread on the 547 here, but maybe it was in the middle of another thread.
I wanted one, but never did get one. I kept holding out for a 3" RB instead of the 4" SB I would see now and the, and missed the boat entirely.
I've often wished they would return, but I don't know if that will ever happen.
Then again, I've seen and heard many complaints of sticky cases/hard ejection and maybe other things I don't recall, so maybe we aren't missing much? I'd still like to try one out myself though.
About ten years ago I purchased a used but almost mint Model 547 3" RB for $400. Still have it and shoot it every now and then. This revolver is wonderfully accurate with 115 and 124 grain FMJ and JHP loads. It shoots to point of aim with either bullet weight and when I'm "in the groove" will give three inch groups at 25 yards using a two handed combat stance.
Never had a problem with sticky extraction. I make a point of running a patch soaked in rubbing alcohol through the chambers before a shooting session. The alcohol quickly evaporates and leaves no residue. There is one problem with extracting the short 9mm cases. If you don't point the muzzle up, the cases will fall off the extractor springs and go back into the chambers. I just point the muzzle skyward and give the extractor rod a good shove and the cases are cleanly ejected.
Other shooters at the range just have to look at and handle the 547. Most of them find it hard to believe that a revolver exists that can eject rimless cases without using full moon clips.