>>716517183
3H is Iron17 and Engage is Iron19 which means either there's a game that started development inbetween 3H and Engage that hasn't been finished yet or it's another cancelled project like the second FE Wii game.

More fun facts: Sacred Stones is Iron9 and Path of Radiance is Iron8 since PoR started development first.
Iron13 is the cancelled Wii game so Awakening is Iron14 despite being usually called FE13.