MESSAGES FROM PLANET EARTH.
A circular silicon disc, manufactured by the Semi-Conductor Division of Sprague Electric Company of North Adams, Massachusetts. 2 inches diameter but with one flattened edge, wafer-thin, one side coated in greenish-purple polychromatic coating, etched lettering "From Planet Earth ... July 1969" visible to the naked eye, and an array of microscopic etching, the reverse irregularly grey-colored, 3 small patches of corrosion to the text side.

A little-known relic: as well as the American flag and the "We came in peace for all mankind" plaque, Neil Armstrong and Buzz Aldrin also left a silicon disc on the lunar surface. That disc was manufactured by Sprague, an established NASA contractor with more than 50,000 components in Apollo spacecraft. Commissioned by NASA's Electronics Research Center, it carried messages from 73 world leaders, gathered in a frantic rush by NASA and the State Department in the weeks before the launch date.
The messages were photographed, reduced 200 times, and etched onto the surface of the disc just like integrated circuits. The example carried on Apollo 11 and now on the moon's surface, like its sister in the Smithsonian, was encased in a protective aluminum holder, with eleven sides symbolizing Apollo 11.
It is unclear how many of the discs were produced. In addition to the examples on the surface of the moon and in the Smithsonian, probably only a handful exist. The present example was given to its current owner in around 1972-3 by a manager at Sprague; the owner's employer at the time collaborated with the electronics company. This disc has a broader rim than the version left on the moon, perhaps indicating it is a prototype or trial run. The discs have been the subject of a recent book by Tahir Rahman, We Came in Peace: The Untold Story of the Apollo 11 Silicon Disc (2007).