Yes the copies Challenge have are from CBS USA. I do believe STV have the original masters, because back for its 50th birthday there had clips and there look far better, cleaner.
So do STV still have rights to them? Do they also have distribution rights or is that CBS exclusively?
Yes STV still hold the UK rights to the series, and wish there could bring it back, but that up to ITV. Distribution rights, I dare say there are retained with CBS. If STV wanted to broadcast the older stuff on ITV I think there could, but why would there?
Is the next post dreaded?