Jeweler David Roux-Fouillet designed an air gun rig and a range of specially pellets that are fired into rings, earrings or pendant made of platinum or 9ct gold. The pellets are made up of plastic wadding, a solid disc of metal, following by a diamond or some other material, followed by a soft gold alloy. The gold in front is them squashed between the ring/earring/pendant and the diamond (or ivory, gem, horn etc.), creating the setting. This high speed video shows how the system works …

Pretty cool.

Thanks to Rob for the tip.