What is a paupers casket?

The expression "a pauper's casket" can relate to a low cost casket provided by the government for indigent people.

Sometimes a reusable casket is meant: in former times indigent dead people were taken to the cemetery in a casket with a bottom which could be opened up; then, at the graveside the shrouded corpse was left in the grave while the casket was reused again.