Checking Magellan's product page:
http://www.magellangps.com/products/product.asp?segID=355

If color is any indication you have a model 100.
The feature list for the orange Explorist 100 does not mention magnetic compass.

You do not have a compass in your GPS.

What is presented is a heading indicator. In order for the GPS to calculate direction it requires satellite fix info and motion of at least walking speed if not faster. (the speed shown is zero)

This is not a valid comparison and demonstrates that one really, really must understand their equipment before relying on it.

I use magnetic compass with my GPS all the time. The GPS tells me the heading to go to my waypoints. The compass tells me where that heading really is.

This comparison is like looking at the directional gyro in an airplane that's been parked for a week and comparing to the whiskey compass. It's an invalid comparison.

unimogbert