75! Take a bow, please. Not many are lucky to celebrate their 75th wedding anniversary, so you should be terribly proud of yourselves for being with each other for all those years. The official theme for this year is diamond. I'd urge upon the jewelry again. A ring, a pendant, earrings or simple diamond studs. Awesome, awesome.
Not all of us put in the time and effort when buying a gift, where those who actually do, are the best of the lot. It shows you care and love this person enough to put that much energy behind something that sounds simple, yet isn't.