in reference to a penis, is an appreciating comment which commends the owner on the impressiveness of his gentialia; in the policies of heterosexuality, only used in reference to one's self unless in a joke or sarcasm
Jamie - "Geez thats a nice painting there" *admires*
Curator - "Yes indeed sir, it is in fact the Mona Lisa"
Jamie - "Whoever must of done, must of been super pro"