There is a controversy regarding the correct mastering speed - and therefore the correct key - of Louis Armstrong’s classic 1926 recording “Cornet Chop Suey”. One Columbia/Legacy release has gone so far as to include two masterings of it, one in the key of F (with a length of 2:58) and one in E flat (with a length of 3:18).
The guidelines say that “variations in playback speed” is not a reason to keep separate recordings. However, it seems to me that this case, with a 20 second difference and a whole tone between them, should be an exception to that.
There’s also a question of what to do with the many copies of “Cornet Chop Suey” currently in MB as I am trying to clean up some of the Armstrong catalog. It seems reasonable to me to assume that a recording that is within 2-3 seconds of the 2:58 time could be merged with the “key of F” version, and likewise for a recording within 2-3 seconds of the 3:18 time merged with the Eb version. (This also assumes that the recording can be identified as the 1926 Hot Five performance, and not one of Armstrong’s later recordings of the tune.)