Nelson’s School Series Book Slate for Home and Student Use (London & Edinburgh: T. Nelson and Sons, [1900?]) is an odd structure, a diptych in a case binding. The exterior looks like a standard quarter cloth case binding with printed paper sides. The interior, however, is made from a painted slate-like material. It can be written on and erased. The earliest known diptych is from 14th-century BCE, making the codex seem like a newbie. Is the laptop a 20th century iteration? Long live the diptych!
Peachey Conservation 