yes the black-dark last long. as long as you dont sand, scratch or polish/buff it. its a natural oxidation. by some time all silver will turn dark. cos of the Oxigen and some kind of sulfer in the air.

and yes they first build a Waxmodel and then they put it together with some other wax-models in a "waxtree" then they use some clay or sand to build a mold. they melt out the wax and then fill in some silver. i dont know if the surface is that coarse of the Mold-Sand or if the wax-modell was Laser-sintered. i dont care about that cos the front side was very clean/glossy.