From the Decades of Style website:
A few years before Rosie-the-Riveter went off to work in her coveralls, she might have worn this adorable pair of overalls to the beach. This vintage pattern from the late 1930s has inset pieces at the waist to provide a flattering fit.
Center back zipper at waistline and straight wide legs. Cross-over straps have button closure at the shoulders. Bodice and waist insets are lined. Suitable fabrics include linen, soft woolens and cotton.