That's how it looks with my (early) Pro FS-R:
We can spot:
DC-Jack --> 2x RF Shunt Cap to GND --> 1.5uH Series EMI coil (+ another cap to GND, supposedly) --> Series PTC --> Shunt Reverse Protection Diode (might also double up as Unipolar Transient Suppressor Zener), or vice versa. At this junction we also have a P-Channel MOSFET as a high-side switch which cuts off power to the various subsequent DC/DC-converters in Standby Mode.
The Polarity Protection is essential (the PMOS switch won't protect against reverse DC since it just a shortable diode anyway ;-) And the added PTC prevents the coil and the diode (and the supply itself) from overheating by limiting the reverse current to approx. 1W/12V=80mA continuous.
@ranger4711,
If your device has suffered from a sustained reverse polarity DC supply incident, I would also think that the series coil blew up (disrupting any power input from there on) and the diode itself might still be working (but should be replaced anyway) unless it melted as well, often producing a dead short. Therefore, I'd check for conductivity of the coil and for shorted diode first.
I'd contact RME (or Matthias) directly for (compatible or original) part numbers.