stands for Optimal Cryogenic Omni Sound.
joking. it's a connection system used by Dyna in their older speakers, stands for Optimal Connection System. http://ocos-cable.com/
the speakers are Dynaudio Confidence 3 (not C3, big difference, that's a completely different, also older speaker made by Dynaudio Acoustics). out of production as of ~2000: http://www.dynaudio.com/int/home_loudspeaker_systems/archive/confidence/confidence3.php
the OCOS connector is the think in the middle, resembling an antenna input:
OK. Thanks for the explanation.