Kansas City, MO, precancel handstamp
Bulk mailers such as non-profit organizations often use precancelled stamps. Postal clerks apply a 'precancel' marking to postage stamps used on permit bulk mail matter. Mail matter using the precancelled stamps is only accepted at the post office that issued the bulk mail permit and precancelled stamps.
A marking device used to make only a single precanel marking on a postage stamp is unusual. Ordinarily larger metal stamps that could apply several markings in a single pass were used, particularly at a large office such as Kansas City, Missouri. An example of a 'rocker handstamp' that was more often used for this purpose is object 1992.2002.141.