Without a BIG oven and probably a brick construction, it may not be possible to get the exact same texture. Usually a crisp top crust is from moisture that is sprayed inside the oven while the bread is baking. Sourdough cultures vary greatly and there are probably thousands of subtile strain differences in flavor and texture. The flour used is also important as is the kind of heat used. Wood fired ovens are good as that gives the bread a slight smoky taste depending on the type of wood used. Home convection ovens seem to come close to commercial bread ovens, but not quite. The big ovens are also using clay type ceramic as a base for the baking. The shine is made by using a product that is offered on the King Arthur flour site. Its sprayed on and has a bit of milk and a few other things that help give that shine.

My grandfather as a baker and had a huge oven that had a bar below the wide door opening. You push down on the bar and the oven floor inside 'moves up' and a new baking surface is seen. It had 4 levels inside and my grandfather would make nice crusty sour rye bread in there. It too had an atomizer that sprayed water inside, that he didn't use for everything. He also liked to add black caraway seeds to some of his rye breads and bagles. We has kids would raid the bakery on every visit.

Here is a link that might be useful: Shine from KA Flour

See the other link as well..

Here is a link that might be useful: Sourdough starter link from yesterday.