The Language of Stamps

With the advent of greeting cards came a new way of communicating - the language of stamps. Through this code, a stamp's orientation on an envelope could say so much more than words. After a Hungarian weekly paper first explained this philatelic parlance in 1890, it went on to be taken up by love-lorn correspondents in countries as far-flung as Finland, France, Bulgaria, Russia and Great Britain, and developed new dialects everywhere it emerged.

Two dozen more examples can be found here.