HELYZQ Portable 6cm Small Copper Ruler 3mm Thickened Brass Metal Ruler Keychain Rule : Amazon.co.uk: DIY & Tools
Brass mini ruler 3mm thick 6cm small copper ruler portable metal ruler retro key tag pendant Keychain festival gift
Small ruler (~6 inch) with strange markings. Bought a slide rule on eBay and this small ruler came with it. I can't figure out its purpose. : r/whatisthisthing