This is description of this part:
Top lens group of the Carl Zeiss Jena GF-Pw 10x (25) microscope eyepiece
The most important thing: this is not a complete microscope eyepiece. This is a service part - a component for repairing the eyepiece.
Position of the lenses: this is the first lens group of the microscope eyepiece counting from the top, called the eye lens
Design: there is a concave lens at the top and a convex one underneath
Mount: yes, the lenses sit in a metal mount, part of which is visible on the outside of the eyepiece (the upper part of the eyepiece)
Matching eyepiece: this is a component from the Carl Zeiss Jena GF-Pw 10x (25) eyepiece with a 30 mm mounting diameter
Although this really is a lens group in a mount, the name "top lens" is in common use, because this component is usually treated as one single, integrated lens.
Because this lens is concave on the outside, dirt collects there. Clumsy cleaning then very often scratches the lens. In many eyepieces this first lens is in very poor condition.
This lens is not a spare part for a microscope. It is a part for repairing a microscope eyepiece - and that eyepiece can be used in various microscopes, even ones from manufacturers other than Carl Zeiss Jena. A few microscopes this eyepiece can be used with are listed in the "compatibility" section, but that is definitely not a complete list. You can assume that the Carl Zeiss Jena GF-Pw 10x (25) eyepiece can be used with any microscope from any manufacturer whose microscope head has 30 mm eyepiece tubes.
What is this part needed for?
- if the top lens of the Carl Zeiss Jena GF-Pw 10x (25) eyepiece is damaged, for example scratched, cracked or chipped
- if the cement between the two parts of this lens (because it is a cemented lens) has discoloured or the two lens elements have started to separate
