Simplicity 3382 vintage sewing pattern, dated 1960. 

Misses' One-Piece Dress with Detachable Collar.

Dress has back zipper closing, bloused bodice and slim skirt with soft pleats at front waistline and back kick pleat. Top-stitching details side front seams. Belt is self or purchased. V. 1 has short set-in sleeves and button trim. V. 2 is sleeveless and has a contrasting detachable collar over a self collar and a ribbon bow at front neck edge. 

Size  12:

Bust  32 inches / 81 cm

Waist 25 inches / 64 cm

Hip    34 inches / 86 cm

Pattern is UNPRINTED, unused and factory folded. Envelope is in very good vintage condition.

More '60s patterns here:

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