They flew into Knoxville McGhee-Tyson, too. I still find Pennsylvania Central Airlines stuff here and there (and buy it whenever I can).
In 1957, when this mailable listing of flights and costs (Knoxville to Washington DC – $28 and change) was printed, Capital was flying high with their Vickers Viscounts (eventually foreclosed on by Vickers). Hard times were soon upon the company and it was sold to United in 1961. The piece is 4 x 9″, folded.
This rather small stewardess pinback is Pennsylvania Central Airlines (PCA The Capital Airlines).
Here’s the story on PCA. If the dates are correct on that page, it means that this pin dates to a time prior to 1948, when the company became Capital Airlines, dropping the “Pennsylvania” from its name.
I passed this by at first until the owner of the antique store (a building crammed so full of stuff that only narrow, one-person passageways led from one area to the next) pointed it out as airline related. Glad he did.