What was symbolic about the imaginary porcelain plate?

The imaginary plate is a symbol of excellence and achievment. The plate now belonged to Antoine.... who's earned it whether he was eligible or not. Donnelly once held the recor broken by Antoine.... the fact that Antoine and his achievements were judged ineligible didn't change the facts. Mr. Donnelly's plate (record) had been broken, and there was no way of putting it back together.