Simplicity 4991 vintage sewing pattern, dated ca.1963. 

Maternity One-Piece Dress, Top and Skirt in Misses' Sizes:

Dress and top feature an inverted pleat at center front and a high, round neckline with back zipper closing. V.'s 1 and 3 have a large square collar. V. 1 is sleeveless. V.'s 2-3 have short set-in sleeves. Purchased frogs are featured at front neckline of V. 2. Collar of V. 3 top is trimmed with lace and buttons. Slim skirt V. 3 has elastic casing at front waistline and a kick pleat at lower end of center back seam. 

Size   12:

Bust   32 inches / 81 cm

Waist 25 inches / 64 cm

Hip    34 inches / 86 cm

Pattern is UNPRINTED, factory pre-cut tissue pieces with perforated symbol markings. Pattern is UNUSED and factory folded.  Envelope has a store stamp and a handwritten name on the front.

More '60s patterns here:

http://allthepreciousthings.com/collections/1960s