Mid Century Modern Desimone Italy Jug - Unusual Glaze

The photos show a recent acquisition, a colorful jug from Desimone of Italy. I'm especially fond of the Desimone pieces that show the influence of Picasso, as is the case here. What I find so unusual is the glaze, which I would describe as "lava" or "volcanic". I have provided two photos that depict the glaze - especially on the bottom. The bottom is marked "Desimone" , "Italy" and the number 09 or 69 - not sure what the number represents, though believe either the artist or motif. Would welcome comments, especially regarding the unusual glaze and any opinion regarding the artist and/or age. Thanks