Courtesy of Alan Pemberton whose useful work has been archived here:
https://www.radios-tv.co.uk/Pembers/...ystems.html#E1
E1
The explanation from the EBU (European Broadcasting Union) is as follows:
The 41-68MHz Band I television allocation was agreed at the 1947 ITU (International Telecommunications Union) conference in 1947, and the first European channel plan was agreed in 1952 at the ITU conference in Stockholm. System B was at that time used by about a dozen stations and only three 7MHz-wide channels could be accommodated within the 27MHz allocation, so they were defined as 47-54MHz, 54-61MHz and 61-68MHz at the top of the band, leaving a 6MHz space empty at the low frequency end. This chunk of spectrum was not officially deleted from the plan until the 1961 Stockholm ITU conference, but in the meantime setmakers and others in the industry seem to have expected something to appear there and had named the other channels E2 - E4.
However, a few transmitters were known to use either 'E1', 40-47MHz, or 'E1A', 41-48MHz, during the 'forties or 'fifties, including ones in Bremen, West Germany, and at the Philips factory in Eindhoven in The Netherlands.