Private printing firms produced all the stamps of the Classics Period. The engravers who created the images appearing on the stamps also worked on projects for private banks, companies, and other countries. The portraits and other images engraved for such clients often resembled those engraved for stamps. 'Printer's Collateral' is material designed for private clients that resembles one or more United States stamps produced by the same printing firm.
The majority of objects falling into the 'Printer's Collateral' category are bank notes that bear portraits of American presidents or public officials, the images having been drawn from the large inventory of dies held by the printing firm. The printing firm used the prepared engravings to produce the images for postage stamps or vice versa.