You may, or may not, be aware that the Electron User magazine was bought off-the-shelf without a cover-disc or a companion cassette attached. Only mail order subscribers to the magazine received a companion cassette. The full catalogue of Electron User discs archived elsewhere are transfers of the original cassettes.
However, there was an interdeterminable period of time where, at a cost of £4.99 each, Pres supplied official Electron User discs by a separate mail order service. Its high cost probably meant only a handful of people took it up, but over the years a few of these 'official' discs have found their way into our archives.
Of course, strictly speaking, this Electron User/Pres archive is unnecessary - all the programs on each of these discs are identical to those featured on the Electron User disc of the same number. There are a few differences though - the format (ADFS 1D00) is the obvious one, the machine code menu system another, less obvious, one.