Jamie and Eddie are shown driving in a Ford patrol car and in the following scene they get out of a Chevrolet patrol car.
Before the in car discussion between Jamie and Eddie there is shot of their squad car driving down the street, the car is numbered 7445 and the hood says "POLICE" when they pull up to the court house to talk Erin they are in a squad car numbered 61795 and the hood says "NYPD POLICE"
Linda mentions how there are 4 ex military in the Reagan family, yet it's never been mentioned that Joe was in the military, only Henry, Frank and Danny.
There was a 4th, Henry's father fought on WW1.
At about 8 minutes, 40 seconds, the PC says, "Sergeant Gormley will start working on your reassignment" when Gormley was promoted to Lieutenant several seasons ago. Also, immediately afterwards, the PC looks at the police academy recruit (who was a prior service Marine) and tells him, "When I have made my decision, you'll be the 101st to know" a reference to the Army. Both items of information are things the PC should know since he was the one who promoted Gormley and having served in the Marine Corps himself.
At family dinner Danny says, "going back to my foxhole". Foxhole is an Army term, in the Maine's it a fighting position. Danny would know this.