Tony Stark created the Mk. V armor after his previous armor was destroyed in a battle against The Freak.
Despite adding small modifications over the years, Stark used the Mk. V armor for the longest of any of his armors and the armor was also worn by several Iron Man replacements, most notably James Rhodes during his time as Iron Man. When Stark eventually returned as Iron Man, he wore the Mk. VII armor and Rhodes continued to operate as a second Iron Man in the Mk. V armor until he was forced to retire in Armor Wars.
Other brief Iron Man replacements such as Eddie March, Force and Happy Hogan also wore the armor.