The listing, Unused Stamp Post Cards from the 1970's has ended.
I'm going to try to explain this as I understand it. In the 1970's and early 80's, they started issuing post cards with stamps already on them. You could just write on the back and mail them.
Here are 3 post cards and 1 Envelope with the postage already printed on them.
9 cents Historic Preservation of Federal Court House in Galveston Texas
10 cents Historic Preservation of Iolani Palace Honolulu Hawaii (1979)
10 cents Landing of Rochambeau, 1780 (1980)
13 cents Golf USA (there is a stain in the upper left hand corner
Shipping is free!