Foam Rubber
One of the earliest materials Peggy Nisbet experimented with, in her attempts to find a material suitable for the construction of her own doll bodies, was foam rubber, and we suspect that it may have been supported on a wire frame or armature. (Exact construction details are not available to us).
Foam rubber doll bodies were made for Peggy by a company called "Dean's Rag Book Co"; although exact dating information is sketchy, we believe that these doll bodies were possibly only in use from 1954 to 1955/56.
We don't know too much about this process, but foam rubber was used by other toy companies to make the "Bendy" toys that were popular into the 1970's.
We only have one such doll in our collection - Over time, the rubber loses its flexibility, and can crack or crumble. (In fact, in the later stages of its deterioration, it can resemble a hard, stale biscuit, which will powder to dust, or turn to crumbs, if handled with anything more than the greatest delicacy of touch).
Our one example, shown below, is approaching her 60th birthday, and is holding out pretty well so far!