I am not certain exactly what this is, but it appears to be an optician’s medical instrument made by the leading 19th century French optical firm of Lerebour of Paris. They were masters of their craft and pioneers in photography and cameras, as well as making top quality telescopes, lenses, and scientific instruments. This piece looks to be late 19th century in date, but it could be earlier or possible a little later. It appears to be rosewood and brass and measures 17cm long when drawn out. The top (where the writing is) rotates to reveal two internal lenses inside, which leads me to think it is a medical instrument for an optician or similar practitioner. My last photo has tried to show this, taken midway between the two lenses. Super quality and in excellent condition.