Postcards are carefully selected in order to give each student a
maximum of exposure to bibliographic richness, varying formats
and levels of difficulty. For instance, at least one card will have
writing on it for transcription. Cards also are selected on the basis
of color or black & white, as well as postcard era (e.g. divided back;
undivided back). In addition, postmarks, publishing information,
trademarks and stamps are considered in allocating cards. A
lecture on the history of postcards provides background in
understanding the evolution of these standards (e.g. see
Smithsonian Institution, n.d.).