At the beginning of the show, Sam is running after the kid on the bike and passes an Orange Chevrolet Corvair with a black stripe. As he is arresting the guy on the next street over, the same Corvair is shown parked in front of the car where Sam is standing.
As Sam and Gene are talking near the East River a Verizon logo sign is seen behind them. The corporation did not start it's roots until 1983.
When Sam is tailing his mother, he jumps out of the car to greet her and the back drop is the Woolworth Building in Manhatten, Unlike all the other shots of downtown NYC, they forgot to super-impose the World Trade Centers behind the Woolworth Building, as they were there when the show was set but not when it was taped.
In the scene where Detective Sam and Lt Gene Hunt are discussing Lt Hunt's history as a dirty cop you can clearly see a Verizon sign. The Verizon moniker did not exist until 2000.