The user "nikusujishichu" over on Wikimedia made a great public domain microscope. I thickened the lines while exporting it to over here, but other than that not much of my work on this one, all credit to said user (although I also deleted labels to make it more universal too.)
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Microscope free icon was designed by j4p4n for icons Png and presented to its users.
j4p4n
10/22/2017