Round Diamond Look Ring Size 5

Preowned condition with some scratches noted when looking under a magnifying glass on the bottom sides of band. Definitely not noticeable when wearing. See pics above showing size on the measuring thingy. (Gosh wish I had better vocabulary!!) I believe a size 5 . It’s a round single stone on a band that might be silver although I couldn’t find any markings. The band itself looks brown or bronze and maybe tarnished silver. It seems I can see some silver in spots. I have no idea if a real diamond or cubic Zirconia or what and I have had in my jewelry collection for years & really don’t ever recall wearing it or how I got it. I don’t have a diamond tester. I’d guess it’s almost 2 carats maybe a little less. It’s got beautiful facets and is very sparkly and again I know nothing about jewelry but when looking at stone through a magnifying glass I don’t see any apparent inclusions or marks which is maybe a sign that it’s not a real diamond..?? I priced this according to Poshmark suggestions so if anyone knows or has some knowledge about jewelry & thinks I am pricing too high or if someone is interested at taking a chance at a lower price I’m certainly open to possibilities or suggestions about determining whether this is real I’m most interested and would be appreciative to help! Bundle for my best deals!