You can tell from the pictures, everything except the buttons and screen has been replaced with wood. I am sure that if the creator has some way of fitting all that tiny font on those small pieces of wood for the keypad he probably would have replaced those too.
The wood probably makes the phone more rugged than plastic, but likely far less waterproof. Its quite a great and well thought out design, I truly like it, too bad they aren’t for sale in the
Russian wooden phone [via MAKE]