I got these at an estate sale. Some of the other boxes and stockings were mismatched according to the box labels, but these two seem accurate. I guess it might be more of a matter of dating the box design than the stockings, maybe? In any case it was a fun find.
Nylon was only very briefly available before the U.S. entry into WW2, so late 40s if they have seams up the back, but if they are seamless, then early-mid 50s.