"Some type of measuring device with a tiny light."
A: "This is a linen tester. Originally used by printers to look at detail/patterns of fine linen paper, now used mostly as a loupe to check registration and close up detail on press sheets. Note the measurements and markings unique to this vs. a normal magnifying loupe, it’s to count the thread pattern of the paper. Totally old school craftsman printer tool. I have 4-5 from my dad. This one is in great shape! Corrected the spelling on loupe."
Thanks Internet.
"... and the liquid will drop through the slit in the middle."
Let's keep it clean; this is not an AO site.