Identifying microscope optic

Ok I'll admit I know nothing about these nor how to read their details, so here is to hoping someone here can enlighten me a little more. My dad got a microscrope out of a sales auction and we were wondering a bit about one of the optics that came with it:

1.6mm
X 115
OIL
N.A.I 30

It has a very very tiny front element to it and we were just wondering about its use/concept/features - ie trying to understand what it is.

I was into microscopes as a kid, and I do remember that oil means that it is an oil immersion optic. That means that you have to get it very close to the glass slide with the specimen and insert a drop of a special oil between to concentrate the light effectively. The oil forms a light guide between the slide and the front element. That's all I can remember however.

Overread wrote in post #12819825
Ok I'll admit I know nothing about these nor how to read their details, so here is to hoping someone here can enlighten me a little more. My dad got a microscrope out of a sales auction and we were wondering a bit about one of the optics that came with it:

Nikon's Microscopy U has lots of beginning through advanced information. There are even interactive tutorials for different kinds of microscopes. You might want to start with the introduction to objective lenses:

http://www.microscopyu​.com …ptics/objective​intro.html

The Small World section has lots of great photos:

http://www.microscopyu​.com/smallworld/