I've picked up a few over the years which I keep near my rig. I think you need to get a pretty high strength one to really see the diamond (probably at least, and ideally more than, 40x) but the trouble with these cheap loupes is the variability in their specs. What's labelled as 40x is sometimes no different from lower spec'd models. If anyone can point to a reliable model of that strength, with a lens that is large enough to use (the little 10mm ones are near impossible for me) that would be a great. Not used one with a built in light, maybe they help, I use a small torch angled to view on the platter.