​If there is any non-chronological way to measure the growth and age of the generation-defining Marvel Cinematic Universe, it's in how the Iron Man suit technology develops. 2008's '​Iron Man' was the first movie in the franchise, and the sleek, weaponized flight suit that Tony Stark built for himself was a huge selling point that featured in some of the first of Marvel's signature well-paced action scenes.

As the films went on, even outside of the '​Iron Man' movies, Tony's armor gradually grew more advanced and powerful, to the point where he didn't need to be wearing it to operate it, could hide parts of it in everyday equipment like a watch or t-shirt, and he even had a model made of nanotech that could shift and morph at his mental command.

But it is clear that Tony's advances in engineering aren't going to stop anytime soon, as a new photo from the set of the untitled 'Avengers 4' shows. Posted to Instagram by GeekPowerBackup, the image shows a large, futuristic barrel resting atop a dolly. While it ​initially appears to be an afterburner of some manner of spaceship, it also bears more than a passing resemblance to a classic Iron Man weapon: the proton cannon.

Originating in the popular 'Marvel vs. Capcom' video games, the proton cannon is a giant, shoulder-mounted laser emitter which produced a wide and destructive beam of concentrated energy and heat. It eventually made the transition to comics where it became a scarcely-used resource due to its catastrophic effects.