The Pyefinch microscope has six screw-on objectives

The seven Pyefinch objectives. Here is an image as seen through objective #5

The support pillar is inscribed with numbers corresponding to each objective.

The objectives consist of a single biconvex lens mounted within the brass objective case. Spherical aberration was reduced by the use of an aperture. The highest magnification lens is fixed in place with a brass retaining ring.

Objective #5 disassembled

Objective #5 aperture