A French Ebony and Ivory Scrivener's Knife.
This tool is made up of 3 parts that screw together, encasing the steel blades and bodkin to make it safe to carry.
As can be seen the end is removable to reveal a bodkin or pricker for making holes in parchment to bind. The steel blades are housed at the widest point of the tool and screw into a steel section fitted to the top of the cap. Originally there would have been 3 different blades but only 2 remain. The blades would be used for cutting quills and scrapping paper or velum.
By it's nature this tool was made to be portable and is neatly self contained. Early 19th Century.
A similar example in black horn and ivory is illustrated in Western Writing Implements in the Age of the Quill Pen by Michael Finlay.