This Stanhope (or Stanho-scope) viewer in the style of a pen is made of ivory (very creamy coloured). They are also made from Bone (with multiple vein lines).
The extreme left of the top section contain a modified Stanhope lens inside which is a microphotograph approximately 2mm x 2mm showing a of a view of the Crystal Palace.
These are optical devices that enable the viewing of microphotographs without using a microscope. They were invented by Rene Dagron 1857. He bypassed the need for an expensive microscope to view the microscopic photographs by attaching the microphotograph at the end of a modified Stanhope lens. He called the devices bijoux photo-microscopiques or microscopic photo-jewellery