It was not the first time knitwear was worn as the prime outer garment. Formerly knitwear would usually have an integral collar or a blouse with protruding collars was worn underneath. It is however noticeable that these jumpers knitted from fine yarn were worn in all weathers.
Post war they are often seen in outdoor summer photographs.
Often it will be one half of a twinset; the other half, namely a long sleeved cardigan could be added if needed.

In the next decade fashion added long sleeves and a polo neck for teenagers of the jazz era.

Violet date stamp:18 OCT 1948 • Age about 18 years old  • Estimate: born 1930 ± 3 years