Today, 03:50
The simple answer -
There are two gyro compass driven card instruments. The one on the right is an RMI with one needle for indicating bearing to an ADF station.
The one on the left they call an HSI, but it is a bastardized gizmo to use with the autopilot hdg and nav modes. The HDG bug sets the desired AP heading. The needle will rotate through the autopilot course window selector to indicate that set course. Selecting NAV with the autopilot, it will track that course. I have never seen something like this, but who knows.
Having flown some of these ancient indicators in my younger days (I turned 78 yesterday), I offered some thoughts on some of these types of indicators in my input below.