Does this look familiar to anyone? I found it while sorting a pile of used US stamps. Thought I had come across another Cinderella but there was something strikingly familiar about the image.

It turns out that this is the left-hand portion of the 1959-66 perf. 11 25c U.S. airmail stamp (Scott C59).
Now I can only wonder if it was separated from the rest of the stamp before or after being used.
Has anyone else come across a similar item? If so, maybe we could start a "Pieces of Stamps" forum category.
