This French Box microscope illustrates the use of polished and dyed sharkskin to produce a 'shagreen' surface. This is a rarely encountered form of microscope and also a rarely found type of microscope-tube covering. Sharkskin is much more often used in its unpolished rough-texture state as a covering for cases of scientific instruments including early microscopes. The inner tube of this microscope is covered in a material commonly referred to as Vellum.