Jason Clarke Antiques has dated this piece to the 1800s.
The spike or forceps can be used at either end to hold a specimen in place for inspection. The holder can then be moved back and forwards along the slider in order to focus it against the lens.

The microscope also retains its original morocco leather covered hinged case with blue silk interior and hook and eye catches to fasten it shut.
Often called a fleaglass or pocket botanical microscope, these examples were produced from the Late Eighteenth Century by the likes of George Adams and were famously produced by the maker’s W&S Jones (thus the name). Like most examples, this one is unsigned but is of super quality with knurled brass edges and beautifully turned handle.
A wonderful survivor in superb condition.
Circa 1800
Jason Clarke Antiques has dated this piece to the 1800s.
You can view the stock and full dealer information on the Jason Clarke Antiques Profile Page