From The Encyclopedia of Mormonism
Author: Kimball, Stanley B.
In April 1843 some alleged New World antiquities were presented to Joseph Smith for his opinion. The six 2 7/8-by-2 1/4-inch bell-shaped brass plates with strange engravings were reported to have been excavated in Kinderhook, Illinois, about seventy miles south of Nauvoo (HC 5:372-79). They were shown to Smith because of his claim to have translated the Book of Mormon from ancient gold plates taken from a New York hill in 1827.
The Kinderhook plates created a stir in Nauvoo; articles appeared in the Church press, an illustrated handbill was published, and some Latter-day Saints even claimed Joseph Smith said he could and would translate them. No translation exists, however, nor does any further comment from him indicating that he considered the plates genuine. After his assassination in June 1844, the incident was largely forgotten. Decades later two of the alleged discoverers announced that the plates were a hoax; an attempt to discredit Smith. By then, however, the Church was headquartered in Utah and little attention was paid to these strange disclosures.
Interest was kindled again in 1920 when the Chicago Historical Society acquired what appeared to be one of the original Kinderhook plates. Later the Chicago plate was subjected to a number of nondestructive tests, with inconclusive results. Then in 1980, the Chicago Historical Society gave permission for destructive tests, which were done at Northwestern University. Examination by a scanning electron microscope, a scanning auger microprobe, and X-ray fluorescence analysis proved conclusively that the plate was one of the Kinderhook six; that it had been engraved, not etched; and that it was of nineteenth-century manufacture. There thus appears no reason to accept the Kinderhook plates as anything but a frontier hoax.