Coca-Cola Service Jewelry

I recently bought some service jewelry. I got the pins from ebay for about half of the book price. I got the 5 year and 10 year for $80 total and then the 15 year pin I bought for $60. I got the ring from a local Coke employee she said it was a 10 year ring but I think it could be a 15 year ring because usually each stone is worth 5 years. From what I can tell it is silver or at least silver plated. I only paid $25 so not to much invested.