AD&D Combat Computer Wheel

By popular demand, here's the AD&D Combat Computer that I found with all my old gaming stuff.  This item was cut out of a Dragon magazine (issue #74 I believe).

The idea was to line up the arrow with the target's AC (the inner ring of numbers) and then compare your character level (colored bars) to the outer ring of numbers to find your target number on a d20.  It even included all the weapon/armor class adjustments if you needed them.

As you can see, I fastened mine with a metal brad that's actually not too rusted after all these years.  I doubt I actually used this device in play.  Did anyone else have one of these?  If so, did you use it?