What's the significance of the small white casket in the play Sweeney Todd?

Question: What's the significance of the small white casket in the play Sweeney Todd!?
Best Answer - Chosen by Asker:

The other poster is reffering to the black one but the white casket represents Johanna,the new chair,his wifeWww@QuestionHome@Com

it is the center of the entire play!.

-in the beginning sweeney rises from it
-it is used as a prop for the whole play, as a table, or anything
-sweeney goes back in it at the end of the playWww@QuestionHome@Com