Unusual Antique Brass Optical Lens Telescope Optical Sighting Scope

  

Unsure exactly what this is, but it's an antique scope, with cross hair and a level attached. Obviously designed to screw onto something, tripod or similar. Measures 20cm-22cm depending on the sight being extended. In original fitted wooden case with the original strap and key!

I'm sure someone will know exactly what it is, but I can't find anything similar online. Original opticians sticker on underside of lid.