This is Keshava Vishnu.
Keshava means His hair is curly and black.
I have heard many times that Krishna (or Vishnu) is very merciful, however, as He holds different objects on His hands - Mace, Discus, lotus flower and Conch-shell, so His mercy can be given in different ways.
Generally the lotus flower and the conshell are for devotees, so to say - an example of lines I have heard.
the question is:
where in the scriptures is this described?
in anyways, Keshava Vishnu, (or Krishna) is always beyond the reach of our material senses, and we can never understand the full picture.