This is plastic wheel, with semi-transparent rotating discs attached to both sides. It is used to determine attacks using different weapons against different AC values. The cardboard sleeve contains instructions for using the wheel and other reference information: "To Hit modifiers", "Damage modifiers", "Armour Classes", "Armour Class modifiers", "Protection from Missile fire", "Fighter's progression", "Weapon Proficiency" and "Parrying".
As might be guessed from the spelling of "Armo[u]r" on the wheel, this was made in the UK and has a small "MADE IN BRITAIN" sticker attached. The sleeve has a subtitle "No. 1 Fighters, Paladins, Rangers and Bards", but this was the only wheel produced.