This is the completed box!
I made a model of the box in FreeCad, 3D printed it out, and cast it in pewter. It is the first thing that I have made this way, so there are some defects in the workmanship; especially in the finish of the box and the quality of the top engraving. There is also a lot of pitting. The engraving is of my wife's old dog, Heiker. I sketched it, scanned it in and vectorized it, and applied it to the 3D print by using the difference of two models tool in Prusa Slicer. The liner is hand-sewn from velvet.
Casting it was the most difficult step. At first I tried to create plaster molds to cast into, but it required re-creating the mold evey time I needed to adjust the sprueing. I found a hig-temperature casting silicone that ended up working better. I was able to cut extra sprues into the mold after setting, because the material is pretty soft. I used something called MoldMax Plus, which is available from Amazon.