Dick the insert appeared to be steel just inserted. Actually the Lt Col posted pics of the sectioned barrel on Culvers.  It didn't work out, blew gas back through the action everytime he shot it.  Looked like a section of steel wedged into a barrel that had been demilled by hogging out the chamber, then the inserted steel chambered, with a big gap before the rifling started.  It shot real good after he put my barrel on it.

The answer to 1903 cartouched Italian walnut could be using up leftovers shortly before the end of production, or it could be the supplier brought more of the wood in at that time.