From the Decades of Style website:
A pair of sleeves to go over something sleeveless is precisely the point of this 1940s vintage pattern. This elegant bolero is perfect over a camisole, tank or even strapless gown.
Slim fitting long sleeve with vent at wrist edge. Long or short sleeves. Optional lining. Slightly built up back neckline is pleated. Pleats release at shoulder seam.