I was involved with the recording industry in the 1960's, so perhaps I can clarify the 'Emidisc' situation. Bands/Groups/Artistes would either hire private studios, or be given Record Company studio time, in order to make practice, experimental, or demonstration recordings. The finished recording would be on a 'recording industry standard tape'. This was far too wide for a domestic tape recorder and played at a different speed. The performer(s) would be given the options of purchasing copies of their work on Industry Standard Tape, Domestic Reel to Reel Tape, or Acetate Disc. To the best of my knowledge, the only blank acetates used in the UK were Emidiscs. The recording was not 'pressed' onto the acetate, but individually 'cut' by a machine. This resembled a record player that worked in reverse. Putting it simply, sound was transferred from the Master Tape to a diamond cutter that vibrated, and cut the grooves. This was old technology that dated back to Edison recordings at the beginning of the 20th Century. If six copies of a double sided single were required, you had to wait while the machine performed twelve times. This took time and these demo discs were not cheap! I cannot ever recall any of these acetates being given matrix or run-off numbers. The self-adhesive labels were provided separately so that any info could be typed on them. These were always blank except for the printed Emidisc blurb around the rim. Any catalogue numbers were typed on by the performer’s management and were nothing to do with Emidisc or EMI.