artictle that gives an overview of the history of unmentionables in the 1950s and 1960s. Read it here...
What i learned also is that the pantyhose is an invention of the late 1950s but was brought to the market in the 1960s. So Ladys of the 50's only girdles, garter-belts and stockings are allowed.
Wikepedia knows about this topic:
In 1953, Allen Gant, Sr., of Glen Raven Knitting Mills developed a commercial equivalent to these hose that he named "Panti-Legs", but these were not brought to the open market until about 1959. During this time, Ernest G. Rice invented his own design for pantyhose (similar to those worn today), and in 1956 he submitted a patent titled "Combination Stockings and Panty".This design was adopted by other makers, and this caused disputes in American courts for many years before the patent was upheld some time after Rice's own death.
Up until this time, there was little reason for women outside of show business to wear "panty hose". However, during the 1960s, improved textile manufacturing processes made them cheaper, spandex (or elastane) made them more comfortable, and the miniskirt made them a necessity to many women. In 1970, American sales of pantyhose exceeded stockings for the first time, and it has remained this way ever since then.
Here is the complete entry.