::He/She is referring to explosive devices that both the Allies and Axis spies used to set fires and for other sabotage during World War II, and also used in other operations by spies and terrorists, guerrillas. These look like ink pens, even function AS pens, until a certain action is performed, then the pen explodes and/or sets things on fire. During World War II, the FBI seized some of these from enemy agents that landed in the US. Assume Good faith please, and sig your statements with four ~s.