I know that during the 1800's and probably before that some portable writing desks held a secret compartment ans was used for spys carrying important papers..Also like in the POTC movie some drawers and trunks had secret compartments. But like Pearl said your best bet would be to check an antiques dealer or someone who would specialize in information on ships in that time period..As for the desks I believe the french made them and the locks could not be picked. The desks were literally torn apart...