The pitting is a result of the casting process and a natural part of it due to the thickness of the aluminum. It was described in above and you can see it in the final prototypes. Some castings have more pitting, others less. It can't be controlled from what I've been told by the foundry. (You can cast with less pitting if you do the lost-wax method, but then we're talking several times the cost.) I actually go over all the pits and fill them in with a pigment wash along with the stamps so that they become more visible.
Also... see this screen from the show, with HUGE pits:
(I'm guessing those are cast pewter or something.)
The pattern and stamp will look a little different in different lighting, and small variations in tone in the metal affect it too. The (imp symbol) stamps have been getting a little darker in the final copies as I've been going because I actually managed to get the pattern to stay on many of them, which isn't always possible- it's going to vary a bit as , again, I don't have full control because it's not an exact process and I'm doing almost 50 of them. As mentioned above, each one is a hand-finished so they will not be exactly identical and that's part of their charm. These are very "living" pieces in that respect, as opposed to having a flat, perfectly symmetrical machined look that doesn't capture the general feel of the screen prop. This is, as far as I've seen, the only ingot replica out there that actually looks like a metal casting and not a "stale" machined piece. (Note: A lighter stamp can be achieved after final processing with a little sanding or rubbing with steel wool, if desired. Acetone will also remove the pattern from the Imp symbol, but I'd be very careful so that it doesn't get on the rest of the surface.)
