COMAND is called with different names, I think now it got one new.
Since you have navigation, the shark fin aerial would have the GPS antenna. It used to have a phone antenna too if it had GPS, I did not check this for new cars but since new cars have BT HF support, it could be that the phone antenna is only included if the car has the comfort telephony option.
If the car has the option 228, AUX heater, this too would use the shark fin antenna.
If the car had satellite radio (US/Canada I guess), the receiver antenna should also be at the shark fin.
I have similar question. Just bought C220 52reg, with shark fin, however I don't have either navigation or phone (just buttons on steering wheel). The question is, what is that antenna for? (unless it's just a dummy, which would be odd)