Cabinet Card or Cabinet Photo - Art ephemera, style of photograph which was universally adopted for photographic portraiture in 1870. It consisted of a thin photograph that was generally mounted on cards measuring 4 ¼” by 6 ½ inches. Usually included extensive logos and information on the reverse side of the card to advertise the photographer’s services.
City Gallery offers an extensive description of cabinet cards.
A wonderful collection of altered cabinet cards are found at Something Sublime.
