Aquakey makes compasses for boats. When you mount a magnetic compass on a boat or plane, there's a procedure for aligning the compass to "true north" against "magnetic north". Essentially what you're doing is aligning the compass heading to the craft it's mounted on to make damned sure that your boat/plane is headed in exactly the direction the compass says it's heading. Any magnetic deviations over long distances can then be taken off maritime charts and then the compass heading and deviation is calculated to give true heading.
Not only is this done during initial installation, it also has to be realigned periodically because magnetic north wanders around over time. This alignment is called "swinging" a compass, and it requires a nonmagnetic tool (usually a screwdriver) to turn the dial.
http://terrax.org/geography/compass/compass.aspx
Even though magnetic compasses are still being manufactured, sold and used by private pilots and sailors, with the advent of GPS they've been rendered little more than romantic artifacts of yesteryear. I don't know for a fact, but I suspect they probably aren't even being installed on commercial craft anymore.
Which might make your key even more of a collector's item over time as magnetic compasses go the way of typewriters and vinyl records!
ADD:
Re: "Aquakey makes compasses for boats"
Oops. Make that "AquaMETER makes compasses for boats" ;-)