Marc Pingoud - Davidships's reply is precisely what I mean. Thanks.

No mention on their website that the vessel is built/rebuilt to spacific Classification Society rules - for many aspects none of them will have developed any yet. But I do note the heavy involvement of insurance companies in the project.
http://www.energy-observer.org/en/

MJ Chow - I'm a little uncertain about your question: Do you mean if there is a classification for her as a sailing ship?

Just curious, is vessel of such kind Classed ?