Nope it's a circular dial which helps you calculate your favourite weapon's Damage, Space Required, #Attacks, THAC0 and AC target number.
|Obverse (Front): Battleaxe to Footman's Pick|
How the heck do you use it? I hear you cry.
You find your weapon of choice around the rim (all the weapons are there, some on the front and some on the back) and then dial in your level using the inner wheel. When your level and weapon are aligned your AC bonuses appear in the middle window. Simples...
|Reverse (Back): Horsema's Pick to Voulge and Missile Weapons|