An oak Desk Letter Box.
The Letterbox has a glass viewing window to the front with the posting slit to the top. It also has a raised brass 'Letters' plaque to the top. It is constructed with open dovetails to the sides and a thumb moulded edge to base. The underside has a worn, thin leather skiver to protect any surface it rested on.
Letterboxes for both personal use and in hotels and clubs were common in the Victorian and Edwardian times to collect the mail for delivery to the Post Office. Given the size of this one it is likely it was used on a desk. Circa 1900.