How do I calibrate an Airguide auto compass?

Here's a thread that asked the same question:

https://www.askmehelpdesk.com/cars-t...ss-102853.html

Here's another site that claims to use the same principle. I've quoted the relevant section, below.

http://www3.sympatico.ca/bkeevil/mer...rch/parts.html

"The compass screws into the lid of the glove compartment with a single screw. A sticker in the glove compartment lists the following instructions on how to set the compass. Airguide in Chicago made compasses with the same NS and EW adjusting screws.

* ADJUSTING THE COMPASS
DO NOT USE STEEL SCREWDRIVER
(THIS WILL AFFECT THE COMPASS MAGNETS)
USE A DIME TO TURN REGULATOR SCREWS
* 1. Head North. Turn the regulator marked NS, very slowly, until the dial reads either N or S.
* 2. Head East. Turn the regulator marked EW, slowly, until the dial reads E.
* 3. Head South. If the compass does not read exactly on "S" -- Then turn the NS regulator just enough to remove only one-half of error.
* 4. Head West. Turn EW regulator just enough to remove only one-half of the error. Follow the same procedure as in step 3. "