In the 1930s, Madame Grès (1903-93) became known for her exquisitely draped, bias-skimming gowns. The successful label adapted, over decades, to changing styles and eventually producing modern cuts for women in the 1970s and 80s. These simple day dresses feature refined cuts and quiet elegance in ultimate simplicity. 

A similar example resides in the collection of the Costume Institute of the Metropolitan Museum of Art, acc. 1996.128.3a–c.

Haute Couture cream cashmere midi dress with attached neck tie, draped back neckline, raglan long sleeves, gathered back waist line, side zipper closure with snaps, and matching cream cashmere belt. The unmarked pin (featured in the last image) comes with the dress, but it remains uncertain if it was original to the design. 
Label: Grès Paris 
Size Label: Unlabeled
Style/Serial No.: Unlabeled

Approximate Measurements:
DRESS
Shoulders: 18.25"
Chest: 34"
Waist: 26.5"
Hips: 33"
Length (high shoulder point to hem): 49.25"
Sleeve (center back neck to hem): 33.25"

BELT
Length: 65.5"
Width: 1"