What to do with redundant engagement ring?

I don't know how to make voting buttons, but please can I have opinions on what to do with my much loved but kind of redundant engagement ring. As I've struggled to find a wedding band that matches (i mo) my engagement ring, my partner and I decided to buy a perfectly matching, and second hand so great value bridal set. I won't start wearing the new engagement ring until the big day, and I'll never call it my engagement ring, just the matching ring! We have thought about simply placing original ring on my right hand, or my partner having it made into a necklace as a gift for the day. Does anyone have any other ideas? It's a 9 carat white gold, 3/4 carat princess cut diamond solitaire. Thanks for any advice/ideas anyone has!