Simplicity 2911 vintage sewing pattern, dated circa 1959.

Misses' One-Piece Dress with Detachable Neck and Sleeve Trim:

Dress has rounded neckline, kimono sleeves and a slim skirt with soft pleats at front waistline. Skirt and bodice are joined to a shaped midriff. V. 1 features contrasting detachable neck and sleeve trim. V. 2 self fabric bows trim dress front.

Size   12:

Bust   32 inches / 81 cm

Waist 25 inches / 64 cm

Hip    34 inches / 87 cm

Pattern is printed, neatly cut with pinking shears. Envelope is age tanned, has light wear around edges.

More '50s patterns here:

https://allthepreciousthings.com/collections/1950s