In a general sense, the term "incunabula" can be used to refer to printed works of a time so early in the history of printing in a given locality that such printing may be said to be in its infancy; thus it is possible to speak of American incunabula, Arizona incunabula, etc. With regard specifically to printing, however, and unless stated otherwise, the term is used to refer to the products of the European press of the 15th century.
Incunabula were usually simply bound in leather-covered boards with decoration in blind. However, their collectors later often had them rebound in more sumptuous covers; consequently original bindings are now relatively rare. (69 , 140 , 255 )