Avira, people will see that I am Jewish just by my name! Who else would always ask questions? As r Steinsaltz haya omer: Eskimo have 100 synonyms for snow, Arabs for sand, and Jews for question.
I was not clear about nafka mina: I am asking what is practical difference for us when returning an object to a jew or a nonjew. What I can see: anonymity. Maybe also returning something that will embarrass a Jew, say who stole that object. What else?