Originally Posted by Sator
Perhaps you are reading a different edition but this is what I found:http://www.bartleby.com/95/34.html
"The business suit or three-piece sack is made or marred by its cut alone."
That sentence implies she used the term "sack suit" as the American equivalent of the British "lounge suit".
Ah, perhaps she is using the terms interchangeably. The passage that confused me was from the 1955 edition:
"Merely to clear away much confusion: Semi-formal does not mean women in formal evening dresses and men in business suits. In communities where the tail coat is worn, semi-formal means dinner jackets (tuxedos) and simple evening dresses. In others where the dinner jacket is formal, semi-formal would mean men in dark sack suits and women in so-called cocktail dresses."
An incorrect illustration of a "sackcoat" in the 1997 edition showing what seems to be a shawl collar tuxedo didn't help either.
Thank for helping to clear this up.