To quote the Wiki Entry: The traditional Opinel knife has a beechwood handle and a high carbon XC90 steel (acier au carbone) blade. Opinel also offers most of its models with a Sandvik12C27M stainless steel (acier inox) blade. Custom Opinel models are available using luxurious or exotic handle woods such as oak, walnut, olive, rosewood and stained hornbeam, as well as other materials such as cowhorn. The Opinel Slim Effile series uses a tapered handle with a slender clip point blade made of Sandvik stainless steel, and the handle may be obtained in a variety of different materials, including bubinga wood, olive wood, and cowhorn.
I use a stone then a few swipes on a ceramic rod. Ronin is right on, carbon tends to rust so make sure you keep it oiled. The plus side of that is it sharpen easy. Great knife, great buy. Way under rated knife for the price. What # did you get ? I have no. 7 & no. 8