What antenna is this?
Personally I'm also almost certain that this is a folded loop antenna. It's really similar to this one (found at http://ok1ike.c-a-v.com/soubory/200anten.htm): 



The only differences between the two lie in the fact that yours doesn't use capacitive coupling for tuning (because it's obviously tuned for a fixed frequency) and the target frequencies are completely different too. In fact I'm almost certain that what you have is not an FM (nor VHF) antenna because it's way too small for that. My guess would be some early Wi-Fi, some GSM or (since you said that it comes from older equipment) even WiMAX design whose wavelengths could roughly match the dimensions of the antenna based on your picture. The ground plane could be there for extra shielding against interference, perhaps to improve reception (obviously this is not a TX antenna).