Frieren's ring from Frieren, Beyond journey's end.
If you 3D print it in resin it is possible to use it to cast a real ring using steel or silver (or even gold if you love your partner so much!).
The inner diameter is of 15 mm but if you need to scale it up feel free to ask me. The little spheres on the back of the ring are a little out of scale but they have dimensions made to be 3D printed.
Feel free to ask me anything here or in the DM of my instagram page "INFEEL_3D:
https://www.instagram.com/infeel_3d?igsh=cGl0aHB0eHh2MnN4