The device was part of a high school biology lab many years ago, and came into my possession when the building was re-modeled and upgraded. I was working in the School District's electronics/AV/computer lab at the time. The high school sent in a large amount of old lab equipment for disposal, so I was allowed to take home any of it that I wanted, because it was destined for the trash dumpster, anyway.
This device hasn't been used around my house since my kids were in elementary school back in the early 90s. We used to go out to a nearby pond, gather up a jar of pond water, take it home, put a couple drops on a glass slide, and spend hours looking through the eyepieces at all the interesting little critters swimming around.
I now recognize this device as perhaps another excellent visual enhancement tool for the model rocket workbench.
It does possess one small problem, though...
The focusing mechanism travels only so far before it reaches a spot where it will no longer move.
Time to get into mechanical tinkering mode.
After figuring out how to dis-assemble the piece, my suspicions were confirmed. A section of the brass rack that runs the focus arm was missing a number of teeth, so the mating pinion gear had nothing to grab onto in that one spot. Doubtless, this was caused by all the use and abuse from numerous high school students over the years it spent in that old lab..
I consulted a McMaster catalog I have hanging around at my workplace to see if I could find a replacement rack. They had ones with the proper width and tooth pitch that I require, but were only sold in 48 inch sections that cost around a dollar per inch!
No good...I wasn't about to shell out 50 bucks for what would amount to using a mere 5 inch section of rack material on an obsolete old microscope.
So, I had to settle for pulling the rack off and turning it end for end, so that the stripped section was away from the most-utilized focusing area. It works fine, but I just have to remember not to crank the focus arm up too high, else it will get stuck in the dead spot at that point.
While I had the unit apart, I was able to glop a little machine grease on some of the moving parts, and even fix a problem with the on-board incandescent illumination lamp.
The last detail to fix was to find some replacement rubber feet for the microscope's base. The originals were long-lost. This one required a little bit of 'McGyvering' as well. Just so happens, I have a plastic bag containing an assortment of rubber feet that came off of various pieces of electronic equipment. The bag yielded a set of four that fit perfectly. A little super glue and all is well.
I now have another fine optical aid to help in making detailed parts for all those upcoming scale birds.
I might even do that 'pond water critter' thing again, except this time with my young grandkids......