Looks like an old school desk top. It has the board that’s been cut(router) in to the board so pencils or pens don’t slide off. I had one at home that I found in the trash can at the old school. It was adjustable, apparently they realized back then all kids aren’t built alike or the same size. Try sticking a fat kid in one of today’s desks. Not gonna happen, and if it does they’ll be heaving for breath half the class.