An early 20th century dental file used to separate teeth. which works on a similar principle to a miniature hack saw but the teeth are very much finer and the length of the blade is only 30mm.
Tightening the screw at the and of the handle pulls the blade taught or allows it to be loosened and removed. The handle is made from Bakelite. The instrument is signed with an unidentified makers mark. The last picture shows a similar 19th century example with an ivory handle.