The boning is spiral steel, held in calico channels.
The corselette is two layers of cotton lawn and a layer of firmer cotton (not quite canvas but not too lightweight). It also has foam cups and underwires, and the waist is reinforced with petersham ribbon.
The bodice is one layer of silk habotai, one layer of cotton lawn and then an additional foundation layer (with boning) of calico at the front and more lawn at the back.