Err NATO-Restricted isn't one of the highest security ratings. It's one that's sorta kinda a problem if it gets released rather than a "omg oh noes I am so dead if the leak gets traced to me" type problem.

It's also actually a caveated protective marking. The NATO bit tells you that only NATO eyes can see the materiel which itself is marked Restricted.

The trouble is there are at least 3 classification/protective marking schemes that I know of and in one Restricted is used to describe materiel that is called Confidential (or is it Secret? It's been a while) in another.