Please see the most recent updates in the "Where did the .com name go?" thread. Posts number 16 and 17.
I think you are correct in thinking that a DG will have an adjustment knob, but the other way of finding out if its magnetic type is that it will lag when turning in one direction & lead when going the other.Is there an easy way to tell the difference between a Directional Gyro and a magnetic compass? I always assume that if you can't adjust it, it's probably magnetic but if there is an adjustment knob, it's a DG.