Why is the paperweight so important in 1984?

It is one of the few things left from before the Revolution. It reminds Winston that life had once been different - it connects him to the past and to what life used to be like. It shows that while the Party tries to erase the past, they can never fully erase it. "It's a little chunk of history that they've forgot to alter. It's a message from a hundred years ago, if one knew how to read it." (Chapter 4 part II)