Secretary's Desk

Not sure of the origin. Passed from my great aunt to my mom in 1952.Passed to me by my mom. It is actually 3 pieces (original), with wooden dowels proturding into coresponding holes. The book case section lifts off the surface of the desk, and the crown lifts off the top of the book case.  The book shelves are adjustable using a nothched system and  wooden slates that sit in the notches and support the shelves. The pull out writng is leather covered and original. Curious about the original and value. 

Thanks Bill