A note in the Mary D. Doering Archive suggests the adjustable gathering at the front waistline may be connected to maternity. The hat in the image is available in another lot. 

Dull green silk day dress trimmed with blue silk taffeta on tiered sleeves and skirt, front bodice opening with adjustable front waistline, and full skirt.   
Unlabeled
Mary D. Doering Archive No.: DRW.008.1850

Approximate Measurements:
Shoulders: 18"
Chest: 33"
Waist (smallest): 28"
Hips: 56"
Length (underarm to hem): 47.5"
Sleeve (center back neck to hem): 27.5"