I’m also considering an upgrade my cheap reading magnifier to a jeweler’s loupe for better viewing of the stylus condition. Here’s the guidance from the
International Gemologist Society (IGS):
“For gemologists, the 10X loupe (with ten-power magnification) is the standard for hand-held
gem identification. Although you'll find more powerful loupes, the depth of field (the area that's in focus) is so small above 10X that they're hard to use. Instead, use a
microscope when you need higher magnification. With lower-powered magnification, you just can't see as much detail.”
They also recommend a triplet lens, but a Coddington is likely the second best for simply inspecting stylus condition. A higher powered LED microscope is probably better for SRA/VTA determination.