This sportscoat dates to the middle 1920s. The revolution in American menswear in the late 20s really was extreme. From jackets like this – long line, very narrow shoulders, VERY tight to the chest and waist – which offered no forgiveness to anyone slightly overweight, slightly shorter than average, not of the ideal “cult of youth” dimensions, in the late 20s the shoulders got wider and more padded, the jackets shorter, more forgiving to different body shapes.
It’s interesting that in the 20s, when women’s fashions tended, however flamboyant and luxurious the fabrics, towards shapeless sacks which could at least in theory accommodate many different body shapes, men’s fashion was obsessed with one body type – long and skinny. The trousers were even more extreme, with very narrow legs – try getting your rugby player thighs into those! This fashion probably grew out of the cult of youth that followed the First World War, which was rather chastened by the stock market crash, driving men’s fashion in a more conservative, egalitarian, direction.