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This is the one. Several sellers of it. Price varies as does ship time. SHop around.

https://www.amazon.com/gp/product/B00JEKXBQ2/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

Also, when you 'sharpie' a bevel and you think that you've removed all of the ink, this little microscope will confirm or deny that assumption.

I've been sharpening razors for over 40 yrs with good results. Never commercially. Just my own stash. Many, many times though I've had to go back to the hones to get that last 1% out of a blade.
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