The disclosure provides Pt—Cu—P glass-forming alloys bearing at least one of B, Ag, and Au, where each of B, Ag, and Au can contribute to improve the glass forming ability of the alloy in relation to the alloy that is free of these elements. The alloys are capable of forming metallic glass rods with diameters in excess of 3 mm, and in some embodiments 50 mm or larger. The alloys and metallic glasses can satisfy platinum jewelry hallmarks PT750, PT800, PT850, and PT900.