This is an extremely delicate stoneware pot that has been bisque fired and then smoke fired in a jacket of cracked resist slip. The cracks occur randomly as the outer coating is rapidly heated in the kiln. It is then removed at approximately 1000 degrees C and set into a container with combustibles. Once the lid is on, the smoke penetrates any cracks or areas where the resist coating has crumbled away. 
 
Like all smoke fired pots, this isn't fully vitrified (which just means it has been fired to a relatively low temperature and is still a little porous). It just means that it can't hold water without a bit of seepage, which would likely also ruin the smoke effect. Best displayed as it is or with dried flowers.