Yeah, was thinking at least 7 inches, maybe 5 minimum, but the resolution would have to be good too. Not much point in a 7 inch screen that's a mere 640x480.
By the way, do you have specs on the power supply? I know it's 12 volts with a positive center pin and at least 1 amp, but the side/type of barrel connector I can't find. Also, any suggestions on lighting? I noticed that on Amazon, that one you posted is frequently bought with this lens:
https://www.amazon.com/Monocular-C-Mount-Industry-Microscope-Objective/dp/B016NUGHK2/
And this light: https://www.amazon.com/HAYEAR-Illuminator-Lighting-Industry-Microscope/dp/B08CBZZZD8/
Any idea if that lens is any good compared to that one on the eBay link? Or if that light would be any good since it doesn't seem to be adjustable like that other $100 microscrope I was looking at which had the lights on two flexible hands.
Thanks for all of your help. I noticed that the camera and the first lens I mentioned (this one https://www.amazon.com/Monocular-C-Mount-Industry-Microscope-Objective/dp/B016NUGHK2/ ) were on auction at that eBay seller you mentioned, and I was able to get them for $23 and $15 respectively (Hopefully they work without issues... pretty much nobody was bidding on them, but this also almost seems too good to be true.. but near all the items on that seller's page were open-box versions/returns anyway).
Since I was able to get a good deal on those and the seller has some other lenses cheap, do you think it would be a good idea to get some of the other lenses in case that one does not work out?
I was looking at these:
https://www.ebay.com/itm/185383773283
https://www.ebay.com/itm/185383784813
https://www.ebay.com/itm/185383915766
I don't think I will bother with that last one as it seems lower quality than the others (and seems to be the one most commonly included with the camera when bundled together), and that second one I am pretty sure is the one you said you used, but do you think it would be a good idea for me to get those other two lenses in addition to the one I already got in case the one from the Amazon link does not work out well for this or am I wasting money? Waiting to hear back from the seller on their offer to combine the shipping, and apparently I might be able to get an additional 30% off the other two lenses.