This top hat can "magically" produce a variety of objects. Simply hide the object(s) in the secret compartment. Casually show the hat to be empty. When you're ready to produce the object(s), pull up on the ribbon inside the hat and pull out the "magical" object.
You can also use the hat to do magic transformations! For example, hide several feet of magician's rope in the secret compartment before the show. When you're ready, casually show that the hat is empty. Then cut a similar length of rope into small pieces and drop them into the hat. Make a "magical" pass over the hat, then reach into the secret compartment and pull out the restored rope!