Coso Artifact
Found near the town of Olancha, California in 1961 is an artifact that is claimed by the discoverers to be a spark plug. The ones who found it claims it to be encased in a rock or lump of hard clay. Spark Plugs were introduced in the 19th century and examiners say it would be scientific and a historical anomaly if it was encased in a rock that is touted to be 500,000 years old.