Souvenir sheets are one of the more interesting philatelic evolutions. Originally, they were issued for philatelic exhibitions, usually given away, sometimes sold at a small premium. The first souvenir sheets were usually just single sheet stamps with borders around them. Later, souvenir sheets became mini-sheets of stamps. Only in about 1930 did marginal markings on souvenir sheets indicate to collectors that they shouldn’t break them up for singles and by 1940 the format for souvenir sheets that we know today had evolved-souvenir sheets in which the stamps and the borders markings were designed to be kept intact.
Above we illustrate the evolution of the souvenir sheet from the Mt. Fuji sheet of Japan with no border markings and only the format (a sheet of 20, whereas the sheet of the regular stamp was 100) to indicate its special souvenir sheet status. The White Plains sheet was the next evolution, again largely a mini-sheet but with some marginal markings (as an aside, my father told me that even as late as the 1940s he would break up White Plains sheets for singles because souvenir sheets were so unpopular among collectors). And by 1940, the final and current incarnation of the souvenir sheet-a separate issue all of its own.