Is there a 'record' of which formats to which Decca licensed its catalog? Especially in the period of 1956-70? I know records, of course, reel-to-reel tape, cassettes, 8 tracks, and CDs, but are there any other formats with which Decca worked?
This might be a good start, go to the format drop-down box, there's a ton in there. https://www.discogs.com/label/5320-Decca?page=1
You could also go on worldradiohistory.com and archive.org and go through old audio magazines, the ads might tell you what format they were using.