what is the present in christmas vacation

In the classic movie "Christmas Vacation," the present that Clark Griswold (played by Chevy Chase) gives to his wife, Ellen (played by Beverly D'Angelo), is a family heirloom necklace. The necklace has been in the Griswold family for generations and is considered a cherished possession. In the movie, the necklace is stolen by a burglar and the Griswold family spends the rest of the movie trying to find it and recover it.