I came across this 2-page advertisement from 1956 for "Revolutionary New Shoes" made with Lastex. Lastex was a fiber made by the United States Rubber company consisting of an elastic core wound with cotton, rayon, nylon or silk threads. The shoes shown here have leather vamps with Lastex fabric backs so the shoe stretches to "fit your foot like a sheath." Sounds like a great idea, right? Turns out this wasn't the first time Lastex was used in shoes!
From 1938, this ad shows Lastex Shoes. Here, the Lastex fibers are combined with suede for "Shoes that fit-and feel-like a glove!" I'm sure they mean suede-like fabric here, because you could not combine Lastex with leather.....at least I don't think so.
In 1941, Lastex was combined with gabardine to make these shoes. The back of the shoes and the heels are leather, but this was a smart idea during the shortages of war. Here, the shoes are described as "these Fashion Plates flattering your foot as your pet girdle flatters your figure." Pet girdle.....really?????
And from 1950, these tweed jersey shoes are described as "the promise of the many wonderful, glamorous, ultra smart shoes every woman will soon be able to wear."