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The sign accompanying the moon rock. It reads

The Moon rock on display was once part of the much larger "Great Scott Rock," collected by the Apollo 15 crew July 30, 1971. It is about 4 billion years old, older than almost all rocks on the Earth's surface.

The "Great Scott Rock" is lunar sample 15555. NASA's Lunar Sample Public Displays page has a "Complete List of Lunar Sample Displays" PDF which lists this sample as 15555,767.