The back end of an M72EC but pretty sure they're the same ignition system.
The ignition system can basically be a pistol case primed with a small pistol primer that's epoxied inside a plastic cylinder that holds an energetic composition that leads to a small plastic tube/shock tube that then leads into the rocket motor and ignites the propellant via another energetic composition.
Pics are from the subcaliber rockets but it's basically the same primer ignition.