These are the discus, club, Sranga bow and the conch of the intelligent Krishna. The Kaustava jewel appears beautiful (on the breast of) Krishna.
एतचक्रं गदा शाई शङ्खः कृष्णस्य धीमतः। अत्यर्थ भ्राजते कृष्णे कौस्तुभस्तु मणिस्ततः॥