Not a lot, but I have heard of these before. people put the Kennedy on there for some reason, to show the similarity between the two presidents. All the wacky coincidences between the two, like-
Kennedy had a secretary named Lincoln, and Lincoln had a secretary named Kennedy.
Lincoln was shot in a theater and his assailant fled to a library (or similar) Kennedy's assailant shot him from a book depository, and fled to a theater.
And so on- number of letters in their names, etc. All hokey stuff.
Anyways neat find, I have known about these for years but have never found one.
There is probably a post on here from the past covering this very subject, I seem to remember one surfacing not too long ago