Maintenance
Focus
Discusses different types: http:www.mindspring.com/~smskjc/framek.htm
Infinite
Adjusting infinite focus system: http:www.janrik.net/MiscSubj/2007/MicroscopeCleaning20070425/MicroscopeCleaning_ausJenaLaboval2.html
Finite
JM microscope is finite focus system. Basically a fine pitch leadscrew slides larger one instead of turning it