As I recall, the series E was the first line of lenses that Nikon targeted for lower priced SLRs. So maybe 'E' stood for 'entry' or 'economy'. I think they were decent lenses but not as good nor built as robust as the regular AIS lenses. According to Wikipedia, the Series E lenses were labeled 'Nikon' rather the 'Nikkor' name given to the pro lenses. I never owned one myself although I still have some Nikkor AIS glass that I love.
