I was looking for a small and lightweight microscope, and found a Columbia FM 600, a field microscope built for US Army by Columbia Instruments (USA) and Swift (Japan). Interesting essay about the history of design and production of this microscope can be found here:
https://www.microscopy-uk.org.uk/mag/ar ... uction.pdf
The microscope comes in a custom suitcase. The scope shows very minimal signs of use – there are no scratches or wear on the stage surface, knurling on metal knobs are clean, and spring-loaded tips of the 40x and 100x objectives show zero scratches. Overall, excellent condition. It is much smaller than my Olympus CH-2 and Meiji MT5200H – see photos. It weights 4,15 kg (9.15 lb.) – about half of the Meiji.
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The microscope: It looks like a later, updated design comparing to the article above. It comes with WF 10x – 18mm eyepieces instead of 15mm eyepieces in earlier FM 600. This microscope uses a standard incandescent 120V, 30W bulb made by Swift instead of the original custom modified bulb. The bulb provides plenty of light, but there is no dimmer included. Since this is a regular lamp, any $15 dimmer will work just fine. Lamp housing, however, get very hot quickly! I removed the lamp housing and placed a Duracell LED headband lamp powered by 3 AAA batteries instead, and it is even brighter! I will design and build a LED light source to replace this bulb. The objective revolver (turret) is not centered, but tilted about 15 degrees to the right, presumably to provide more room to manipulate the specimen. The removable mechanical stage can be placed on the left side or on the front, I find left side placement optimal. Coarse and fine focus knobs are not coaxial, I need to get used to this. All the controls operate smoothly.
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Optics: It is likely of-the-shelf optics from Swift. A few parfocal shims were installed from the factory (?) I compared the performance to Olympus optics and moved Olympus eyepieces and objectives to this microscope. While both Swift and Olympus eyepieces are marked 10x 18mm, and FOV looks identical indeed, the visible diameter of the image is noticeably larger through Olympus eyepieces. Swift objectives are better corrected for chromatic aberration (color fringing) than Olympus EA (educational achromat) series, but Swifts image is blurred close to the FOV edge. I tried higher-grade Olympus objectives (SPlan 20x and SPlanApo 40x), and they, of course, perform the same as when mounted on CH-2. I am planning on updating all the objectives to SPlan series (I will sell the excellent SPlanApo 40x - working distance is way too small for my applications).
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Overall, it is a nice, solid microscope that you can take along on a trip, especially after upgrading the light source to LED. It will likely replace my Olympus CH-2 scope in my home lab.