Ed:

From the info that I can find, I'm sorry to say that you may never find the info you are looking for, due to several reasons:

As regards the builder, the Baron De Kalb (originnally commissioned as the St. Louis) was one of 7 identical "City Class" boats, four of which (including the De Kalb) were built by James B. Eads at Carondolet, MO. The ribs and armor backing of these boats were constructed with oak. I'm not sure about the wood used for the hull, decking and interior partitions.

As far as the bronze goes, research records that the iron plating, guns and "most" of the machinery were removed by the Navy shortly after the vessel sank.

Regarding the removal of the wreck by a snag boat, all current info indicates that the De Kalb still lies exactly where she went down in 1863. Following her sinking, a sand bar formed above or below the wreck and eventually caused the Yazoo River to change its course, leaving the wreck surrounded by dry land. It can still be accessed today (though mostly buried), but the removal of any part of it will incurr the wrath of the Navy which still claims ownership.

As many other steam boats were sunk in that area by the Confederates, it is highly possible that the wreck that was moved by the snag boat was not the De Kalb.

There was once an effort by a local (Yazoo City) Historical Society to raise funds and get permission to raise the De Kalb but their web site is no longer online.

Legends surrounding artifacts such as you are researching are not uncommon. For esample; some residents of St. Charles, AR, still claim that items marked "Mound City" are still being dredged up from the bottom of the White River. According to them the U.S.S. Mound City (sister-ship to the De Kalb) was sunk there during a fight with a Confederate battery ashore. However, the ship, though disabled, did not sink and was towed to the Navy Yard at Mound City, IL where she was soon repaired and put back into active duty which she continued until the end of the war. Consequently, the items lying in the river could not have come from the Union gunboat.