The anarchist is not a crook.

He is an idealist.
Convinced that the unpainted oblong box would furnish a clew to the man's real personality, Cleggett, assisted by Lady Agatha and Dr.
Farnsworth, opened it in the cabin.
They first took out a number of plates, some broken, some intact, for the manufacture of counterfeit notes of various denominations.

There was some of the fibrous paper used in this process.

There was a quantity of the apparatus essential to engraving the plates.

This stuff more than half filled the box.