This one has two .38 cal rifle barrels over one 16 ga shotgun.
Uses conventional back action locks, right and left.
The right lock fires the right rifle barrel when that little blue steel arm is forward, as in the photo. To fire the shotgun, move the arm back, it transmits the blow of the cock to the lower shotgun, nipple. Hmmmm . . . how does it miss the rifle nipple, you ask? That little webby-part of the cock strikes the blue arm, to transmit the blow to the shotgun cap.