When Petty Officer First Class Armstrong shows his Military ID to the agent at the airport, the ID shows his pay grade as and O-1 (an Ensign) and should be E-6.
As the FBI team moves in while King talks to Marcus and he reads the file discovering the Al-Majid trap, one of the FBI Tactical Officers has a LASER attached to his optics on his rifle, no rifle optics in close quarters combat configuration puts the LASER if attached on the Optics, as it would raise the aim point too high in close quarters combat situations. it would be mounted to the side rail of the barrel.