Audio problem: While at the range, Jamie takes Frank's revolver to the line and fires it. The last 2 shots you can hear the casings hitting the ground, but not on the first 3 shots. The last 2 shots are from another camera angle. Revolvers don't eject the casings, so we shouldn't hear them landing.
Factual error: Danny shoots Frank's revolver, and as he continues to shoot, you hear the sound of a casing hitting the floor, which shouldn't happen since it's a revolver being fired. (00:11:46)
Answer: It is the lapel pin worn by members of the NYPD Honor Legion.
The lapel pin is on Danny but not Biaz, why? Also, Baker, Sid, Frank &Garrett wear one. Significance? Are they all the same?
Is the P.C.'s pin different than a legion pin? What are the symbols and their meaning?
I think it may be Masonic?
But why would the mayor wear one?