My engagement ring was my grandma's. My dad, her only child, bought it for her after he graduated from college and started his career. It was a "Thank You" for all her love and support (and for putting him through college).
I've had a few people comment that Sweet Pattootie should have bought me a new ring. I did that the first time I got married. I wanted to do something different. Plus, I've always loved this ring. The small Tiffany set round center diamond is encircled by lots of little bitty diamonds. It always reminded me of a ballerina wearing a tutu. So it was dubbed "The Ballerina Ring".

I inherited it shortly after my ExH and I separated. When and I started talking about marriage, I knew I wanted to wear this ring.
It was never important to me that SP buy a ring. I'd rather he use the money for something else - like food, or a down payment on a car. And I love that this ring was originally bought with love, even it was a son's love for his mother. Anything from Granny's marriage to my granfather would have been completely wrong to use. My Granny R and my grandfather had a horrid marriage. I have her wedding ring from the 1st time she married him - with the message to "Never make the same mistake twice."

Sissy got the wedding ring with diamond in it from the second time she married my bacon-fed-knave grandfather. Her message was "If you make the same mistake twice, at least get a diamond out of it." Granny R had a really wicked sense of humor.