Conchos are round pieces of metal, usually with two slits in the metal. They originated with Mexican vacqueros who used them on saddles to secure the saddle skirt to the saddle tree. They went from being utilitarian to being decorative and are seen now on clothing, belts, hat bands, saddles and apparently some "belly dance costumes." In the garment you posted above, there are three: one on each side of the neckline and one at the bottom of the vee neck.
These don't have the slits. Several are made to link together into a belt.