I remember knitted suits from my childhood, and they evoke a kind of musty feeling for me, perhaps because they were the favorite outfit of my least favorite high school teacher. This particular photograph comes from the very late thirties or forties, judging by the length of the skirt. Somehow the pleated skirt and the short jacket makes the outfit look a little juvenile to my eye.
Such knitted outfits were made on large knitting machines, the way that fancy clothes by brands like St. John Knits still are today. However, a very experienced kniier could also make her own, like we see in this pattern here.
Perhaps this woman was not only showing off her outfit, but also her skill with the needle.