I’ve encountered someone who has explained a little more of the origins of the different edits. From what I understand:
They first produced a master ‘international’ edit, which runs to about 25m30s. These featured three fades for commercial breaks; one after the opening titles, one mid-show and one just before the end titles. The titles were centred. I am told these should be considered the definitive versions.
From these, a second set of masters were produced that cut a further 2m, reducing the running time to around 23m30s, this was to allow more advertising. These are the ‘short international’ edits, and PAL->NTSC standards converted copies of these were what were originally broadcast in the US.
The ‘UK domestic’ edits were similar in length to the full ‘international’ edits, but with the commercial break fades removed - replacing these with straight cuts, sometimes wipes, sometimes shortening sequences by a few seconds in the process, and occasionally adding brief linking shots to make the transition flow better. These had the left justified credits that included a credit for the guest star.
[There also appear to be a handful of master tapes out there of ‘short UK domestic’ edits, which are the ‘UK domestic’ versions shortened (as per the ‘short international’ edit) to allow an extra couple of minutes of adverts.]
The ‘German domestic’ edits are very close to the full ‘international edits’, but with the opening and closing credits replaced by German language ones. They retain the original ‘international’ cut advert break fades for the most part, and don’t contain the changes made for the ‘UK domestic’ versions. There are a few other changes, an entire extra guest in one episode, a different Waldorf and Statler balcony scene at the end of the Harry Belafonte episode, and possibly other differences.
[There are also other ‘… domestic’ edits in French, possibly Spanish and others, but these have rarely seen the light of day since original broadcast. As with the ‘German domestic’, they are largely based on the ‘international’ cut.]
…. Then Henson acquired the rights and the master tapes. And put together a syndication package. It’s the syndication package that forms the basis of everything that has been seen since.
There is speculation that many of the master tapes had been misplaced at this point, or who knows, it may just be a case of picking up the first tape off the shelf by someone who didn’t know any better. But, the syndication package ended up consisting of approximately 15 ‘uk domestic’ edits, and 105 ‘International’ edits.
[The German market is the only exception, where the episodes are still largely from the original ‘German domestic’ edits. While a bunch of re-mastering work was done for the syndication package, none was done for the German masters, which is why the quality of the German DVDs is not so good]
However, more master tapes than that clearly did survive, as the commercial releases over the years have occasionally thrown in an episode that is not one of the edits that was part of the syndication package.
So, for example, the ‘Season set’ DVDs feature the ‘UK domestic’ cut of the Elton John episode, but the ‘Best of’ DVD sets feature the ‘international’ cut. Most DVD releases of the Charles Aznavour episode feature the ‘International’ cut, but the French DVD used the ‘short UK domestic’ cut.
Another interesting example is the Chris Langham episode, which is one where the syndication package featured the ‘UK domestic’ edit with left-justified titles and edited ad-breaks, and the full ‘international’ edit has never been seen… however the ‘German domestic’ (which should be largely the same as the ‘international cut’) preserves the original ad-break fades… and an extra reaction shot in the ‘shuffling a pack of sausages’ sketch, that would likely be what was seen on the original US broadcast.
… Then, just to complicate things further, Disney acquired the rights and master tapes.
The Disney+ versions appear to be based on the syndication package, which had been extensively cleaned up and remastered for the DVD releases, therefore presenting an eclectic mix of ‘international’ and ‘UK domestic’ edits…
However, there seems to have been a decision to attempt to standardise on the ‘international’ end-credits, as only 4 of the 118 episodes on Disney+ have the ‘UK domestic’ left-justified credits. But rather than switch to the ‘international’ version for the whole episode though, they’ve taken the syndicated ‘UK domestic’ version, and patched on just the titles from the ‘international’ cut, to create a kind of hybrid. (I’m guessing because it avoided more substantial re-mastering of those 11 episodes).
So, from the known high quality sources, approximately 17 episodes are available (or can be reconstructed) of the ‘UK domestic’ versions. 117 (I think) either exist (or can be reconstructed) of the ‘international’ versions.
There are vanishingly few off-airs of any other ‘UK domestic’ cuts beyond that 17 that I’ve been able to find. If they do exist, they’ve largely been pushed out by more recent recordings of the syndication package (likely considered preferable as they would be higher quality).
For anyone interested in more detail… (you’d have to be crazy!), I’m putting together a spreadsheet of episodes, versions, releases, and differences. At least for the stuff I know about.