Although hidden from the camera's viewpoint, it appears the photographer called upon a headrest, or posing stand to help the sitter keep still during the photographic exposure. The presence of the headrest is revealed in the shadow cast behind the sitter. The sun must have been high in the sky when the portrait was taken as the shadow is low in comparison to the sitter.
This portrait was taken during the same sitting as Schaaf numbers 291, 292, 296 and 1297. The same sitter is also photographed in Schaaf number 1264, but wearing a different outfit.