AD&D 1ed Combat Computer

The Dragon Magazine (issue #74) contained a Combat Computer which was an essential tool when playing AD&D 1ed by the book. Now I realize everyone doesn't play with things like weapon vs AC tables, weapon speeds, segments and all that stuff. But unlike some old schoolers the group I play with does use some of this which makes this little combat wheel invaluable during play. Besides, its not like we looked these up during every combat. Every character has their "to hit" charts filled out on their character sheet beforehand, so all you need to do is look up the roll needed. As a DM this wheel makes looking up monsters "to hit" rolls much more convenient.
Taking a page out of Maldin's playbook I modified the combat wheel to include some of the more commonly needed charts on the back of the wheel. This saves on flipping through books during play.

Anyway without further ado the (slightly modified) AD&D 1ed Combat Computer;

Print it out on the best cardstock your printer can handle, or do as I did and glue the two printed sheets to some decently stiff cardboard.  Cut out the two discs.  The outer ring of large numbers on the lower disc should all be visible once the two discs are connected, while the inner ring of large numbers should only show in the "Target AC" window.  Cut out the four windows in the middle of the upper disc too (Xacto knife or razor knife - use caution). As has been commented below, it might be a good idea to laminate the discs before assembling them. Connect the two discs with whatever method you can find that works and allows the two discs to turn on the same axis.

    If you really need instructions for how to use it you obviously haven't played enough 1st Edition and you shouldn't be messing about with such complex tools as this - you might hurt yourself.  To use it, turn the two discs until the AC of the target shows in the window and lines up with the arrow.  Find the curved, colored band on the upper disc that corresponds to the class of the attacker.  Find the column section on the band that includes the attackers level (or hit dice for monsters).  Follow that column out to the outermost edge and read the number required to hit in the same column off of the lower disc.  Note, that common sense must be used here - when you try to read results where the adjustment windows are black you're "off the chart". Weapon-vs-AC adjustments will ONLY be accurate when turning the discs to select an AC between 10 and 2, because obviously you're actually selecting the corresponding armor TYPE at that point, not actual armor CLASS.

Let's try an example here. A 6th level MU attacks a unarmored foe with a dagger. You would line up the inner wheel with the target AC 10, look at the "to hit" needed for a 6th level MU and see that it was a 9 and then subtract the armor modifier for the dagger (+3) to arrive at the final score of 6 needed to hit. 

Easy-peasy right? That is why all the players are requested to calculate their "to hit" charts ahead of time, because it can be time consuming to do in combat situations. As with most things the explanation can be much more complex than the actual process.

Edit 11/1/13 - Corrected the tables on the back. The Cleric turning table was slightly modified from the BTB 1ed. version. That has been updated since this seems to be getting some traffic. If anyone sees any other irregularities or typos let me know.