COP means Certificate of Pedigree which means that he isn't fully registered. They usually give it if the sire was registered within the KWPN but the dam was not. (so for example, my old horse had a COP from the Canadian Sport Horse Association...his sire was registered and approved, but his dam was a TB)
For a gelding it doesn't really matter at all; the COP just proves what his bloodlines are :)
Ohh ok thanks! A gelding I'm looking is a Dutch WB cross. Obviously with geldings it's not particularly important to have papers but it's kinda cool regardless lol.