^I suspected that since I knew he's the one credited with the invention of the puffer jacket as an evening garment but I was too lazy to check if it was his or Lanvin's, since I found the whole ensemble credited to the latter on Pinterest. Turns out that according to the V&A, the gowns is in fact Lanvin and the jacket is by Charles James.
Could a kind mod change the first half of the post title so it reads "Evening Jacket, by Charles James. 1937. Evening Dress, by Jeanne Lanvin. 1935."?