UX11var UPSS# S12e 1c Grant, Blue on White Clean Face, Postal Card "Picture Hanger" variety can be found here: http://postalstationary1.mybigcomme...ger-variety/
UPSS is the United Postal Stationary Society.
If you go there you will see a card image. There is a strong magnifying program. Use it and go to the top of the portrait image where you will see a plate flaw which causes a white hole to be surrounded by frame line. The white hole is where you would drive you nail to hang the portrait.
If I brought the image here, no one could see the flaw in question.
EDIT: Let me add, Goggle is your friend. I copied this part of your text
ux11 "PICTURE HANGER VARIETY"
into a Goggle search box and pressed enter. What I list above was the very first text return from the search. Only images were above that and those images where of no help.