Screw-barrel microscope
This screw-barrel microscope is a single-lens magnifier with a threaded barrel for focusing. Like the hand-held screw-barrel magnifier in the Golub collection, this instrument has removable lenses and a spring-loaded universal sample holder (for either flat slides or glass phials), and uses transmitted light for sample illumination. Focusing is accomplished by screwing the body up or down, which changes the sample position relative to the objective. This instrument has a threaded base, containing a flat glass (non-lens) insert. The entire microscope can be attached to the scioptic ball and used as a projection microscope much like the Solar Microscopes in the Golub collection.
This microscope has two lenses, labeled "1" and "2". When used as a simple magnifier, imaging is approximately 100x.
Turning the base focuses the sample. This is difficult however, since one has to grip the smooth barrel (above) through the cutouts of the base (left). It is easier to remove the magnifier from the base, focus the sample, then reinsert the instrument back into the base.