I love these so much I just have to share them! Despite having a thin stiletto heel already the leather sole on these extends round the shaft to create a sort of shadow, giving the illusion the stiletto is thinner than it really is. Given the period these were made (late 1950's) they could have been designed by Jourdan himself, or his sons who opened the Paris store in 1957. I'd love to find out for certain. The label resource seems to indicate Jourdan senior remained the head of the business until his death in 1976.
Found this advert today, 1955 March issue of Femme magazine, Christian Dior shoes by Delman, showing a similar idea, with the sole extending over the upper at the arch:
