Vintage Penworthy air mail stationary set. It contains a writing tablet and 15 envelopes. Price is for one set and we have several available. Overall good condition, but they do show some wear. There are some stains, small tears (the worst is on one front corner) as well as general storage wear / discoloration. The envelopes may be sticking together and may rip if you aren't very careful in trying to open them.
The history of Air Mail is available in PDF form on the USPS website.