Thats a lovely gift! I've been trying to convince my dad to get my mom something like that. Mom works in a kitchen and one day she was kneeding dough... hours later she noticed the diamond from her engagement ring had fallen out. She KNOWS it was in someone's pie crust We never had the money to replace the stone, but I have always thought he should get her something like your dad got your mom.

I had always thought an eternity ring was a band with channel set diamonds all the way around (which seems silly to me - and hard to keep clean! )