Antique Pedestal Desk with leather writing surface and hutch

I have a large antique wooden pedestal desk. It looks to be Walnut and is solid wood. It has 4 drawers on the left pedestal and one drawer and  file holder of some sort on the right side. There is no drawer in the middle. The top "hutch"  has identical sides with a drawer topped by a cabinet of 12 pigeonhole compartments. In between there is a book shelf. This entire hutch just lifts off - there are slots for everything to fit together very snuggly. There is a large piece of black leather embedded in the desk top for a writing surface. The writing surface part slopes very slightyl down from where it attaches to the hutch. The drawers and file holder in the pedestal only go back about halfway leaving a large empty spot on either side enclosed by wood. I was told these were secrect compartments but other than taking the drawers out there is no way to get to them. The decoration for the key holes are made of wood - either carved out of the drawer or attached some way that is not apparent.I have added a picture of how the drawers are assembled and am wondering what that is called. I am curious at to the age, history and value of this desk. Thank you!