This heart-shaped box is a single print with a built-in hinge that is described by a tutorial by Clockspring 3d under “hinges and hearts in Fusion 3d”. 

I added the ring posts, which accommodate ring sizes 14-18

I also made a smaller one. 

I made this for my wife, who thought it a nice design. However, she announced that she had no idea where her rings were. Oh well.  How can I complain about an 83-year-old first wife?