My grandfather was a chemist, this was found in his estate. What is this?

Sort of microscope for observing crystal formation?

So, the Denver Fire Clay Company supplied a lot of interesting instruments and tools for industrial use. Check this out: http://americanhistory.si.edu/collections/search/object/SILNMAHTL_13859

I'll dig into this further and report back.

Neat: https://archive.org/stream/illustratedcatal00denvrich?ref=ol#page/n3/mode/2up

That catalog is probably too old, but boy is it cool!

Pretty sure I've got it: https://www2.humboldt.edu/scimus/RefracExhibit/SpecDesc/ZeissSugar_oil.htm

It is an refractometer.

Here is your grandfather's instrument explained and with a manual

Edit: scrolling down I see others have found the same link and have solved it -- oh well

From the look of it it seems to be a refractometer. It is used to determine the refractive index of liquids (usually solutions). If you know what kind of solution you are dealing with (e.g. sugar or alcohol for brewing purposes) you can determine the concentration with the help of specific tables. The tube connections are normally used to connect the measuring cell to a thermostat as the refractive index is also temperature dependent. A quick search tells me that your refractometer seems to be an oil and sugar one. You can find more info about it here: https://www2.humboldt.edu/scimus/RefracExhibit/SpecDesc/ZeissSugar_oil.htm

Kind of looks like something to do with film. Carl Zeiss makes camera lenses and other optics. Or some form of refractometer.

I thought maybe a chalkboard eraser cleaner.

Our elementary school had one and I got to use it with our janitor!

refractometer...

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