What does the coral mean to the Party in 1984?

In 1984, Winston finds a piece of coral encased in glass in an old junk shop. It's a paperweight, and to him, it represents the time before the Party came into power, a time Winston dimly remembers from his childhood. Winston treasures this tiny reminder of the old days, even though he recognizes that the old days were not so great.

To the Party, however, the coral represents everything it wants to stamp out. The Party wants people to believe that life was horrible before the Party took over. It wants to control the past. Thus, the fact that Winston owns this trinket is a thought crime. It means his every idea is not controlled by the Party. Even if he had done nothing else, buying this coral--even desiring this coral--shows to the Party that Winston is a criminal who deserves arrest.