The Sinanju Stein was developed as part of the Earth Federation Forces reorganization plan known as the "UC Project". Stein means "stone" in German and Norwegian, and the Sinanju Stein's name was a reference to it being "a jewel in the rough". This mobile suit was created by Anaheim Electronics to test the sensitivity and durability of the lightweight and rigid material, the Psycho-Frame, for use in a mobile suit's internal movable frame. The Sinanju Stein was also equipped with a Psycommu system, and the "Intention Automatic System", which functions by using the Psycho-Frame's sensitivity to the pilot's thought-waves to directly affect behavior of the mobile suit.

The suit boasts high mobility and features flexible thrusters on its legs and backpack, allowing it to achieve precise movements at high speeds. Due to its murderous acceleration, it was impossible for ordinary pilot to control the Sinanju Stein, and its evaluation tests were conducted on autopilot to test the limits of the Psycho Frame.