A DG (Directional Gyro) can be either slaved to a remote device or be what's called a free gyro. The majority of DGs are free gyros. Free gyros are set to the magnetic heading prior to take off and every 15 minutes or so thereafter due to their tendency to precess (drift off heading). If we want to split hairs the compass heading is not necessarily the magnetic heading, but the magnetic heading uncorrected for deviation (local magnetic disturbances in the aircraft). The compass heading is converted to the magnetic heading by referring to the compass correction card (which is required by FARs). The reason to have a DG is to provide a reliable and instantaneous indication of heading change.
To further murk the waters, DGs up until the 60s or so were not normally vertical presentations. They were horizontal (like a big compass card). I had one once in a 1964 Mooney and it was a pain because you had to do all the math in your head.
To get back to the point of the thread, the second vertical instrument in AH II looks like an ADF (Automatic Direction Finder). In an ADF the needle points to an NDB (non directional beacon) or a commercial broadcast station. The needle on an ADF always points to the station so, like the compass in AH II, the indicator in the game works backwards. If you are flying North (which in the game puts the needle on 0 degrees) and make a 90 degree right turn, the indicator should be on 270 degrees (relative bearing).
So in AH II we have two instruments; one that looks like a whiskey compass (or early DG in some planes) but doesn't really work like one and the other that looks like an ADF but doesn't really work like one.
