Because it tarnishes when not worn for a little while, I've had for 8 years and when I bought it, it bought it because it is an overlay, as I cannot have any metal touch my skin or I get a horrible rash that blisters. I had to polish it before I put it up for auction and it is already starting to oxidize. Wearing/using silver continuously is what keeps it from oxidizing. I hope this answered your question. Thank you for your interest. =)