History of Olympic Gold

ET was with the U.S. Olympians in London, celebrating the hard-working athletes who all had one thing in mind -- bringing home the gold.
A few facts about the coveted medals:
1. The gold medals are actually 92.5 percent silver with a gold plating.
2. The last time they were made entirely of gold was 1912.
3. They are 3mm thick and 60mm in diameter.
4. They're valued at around $706.
Watch the video to see Christina McLarty's tour of Goldsmith's Hall, as she gets a rare look at extraordinary gold pieces spanning 4500 years.