When I worked at a local pizza joint (a LONG time ago) we get that effect by lightly covering our paddles with semolina before we dropped the dough on it. The semolina helped the dough release from the paddle and also gave the crust an extra crunch.
Cheers, Christopher A. Kinkade, Griffith, IN USA
"The difference between a cook and a chef is understanding what's going on." - Alton Brown