My grandson is reading the Dragon Master series and asked if we could make the dragon stone.  We found the one made by Nicholas Scroggs, but I wanted to make the band from a different filament rather than paint it. 

Print 2 stones (they are identical), 1 connector and 1 ring, either A or B.

I was concerned with my grandson hanging this around his neck with a significant lanyard and possibly hurting his neck if the stone gotted tugged. So, I designed some breaking points on the ring, Ring B.  If you use this feature, be sure to test it using your print settings and level of safety.  I did not do a pull test on this - that is your responsibility.

The string hole is 4mm diameter.

Print orientations are as shown in the photo.  The only support I used was the hexagon surround as shown in the photo.  There is no need to provide supports for inner space of the stones since the spaces top surface is not critical and spans only 10mm.  The connecting rod length is  5 mm shorter than the space provided in the stone, so there is room for the span to sag.

I printed numerous successfully with 2 perimeters, 10% gyroid fill. The only support used is as mentioned in the previous paragraph.  No brims were needed.

The snugness of the connecting piece will depend on your printer setup.  I designed a 0.1mm gap between the two and glue can be used to hold the pieces together if needed.

The photo of the DragonStone I printed is transparent PETG with only a single perimeter, so you can see the 3D honeycomb infill at 15% fill.