You have correctly identified the first edition of 1925 and the second edition of 1928. There was also a third edition in 1930, a fourth edition in 1933, a fifth edition in 1936 which was reprinted in 1936 and 1937 and a sixth edition in 1939 which was reprinted in 1942, 1946 and a revised reprint issued in 1948. I do not know of any further editions. Perhaps someone else can complete the story.
All editions have common features such as the four stroke cycle and illustrations of the flywheel clutch etc. but there are also differences between all editions some of them quite major.
I have the first edition, 98 pages, the third edition, 124 pages, the fifth edition 1937 reprint, 96 pages, the sixth edition 1942 reprint, 80 pages and the sixth edition revised reprint of 1948 with 82 pages.
The third edition is the most liberally illustrated of those I have with pictures from CW through to the 350, 500 and 600cc models of 1930 plus details of DT, SW, and others. There is no specific picture of the EW although its successors are shown. There is an illustration of the lubrication system for the 1928 350cc models.
The first edition has no mention of the EW and concentrates mainly on the 2.3/4hp models with mention of OB,OW and RA models.
I cannot speak from knowledge of the second edition but it is a fair bet that the EW is most likely to be featured in the 1928 issue. Chris