The "U.S.A. 1996 A.D." plaque is a garbled version of the plaques built into the 1972 Pioneer 10 and 1973 Pioneer 11 space probes, the first man made objects to leave our solar system. The garbling changes eliminated the size of humans relative to the probes, the length of the units used to specify distance, the location of our nearest pulsars, and our distance from the galactic core.