I think the .470 Capstick was only catalogued in 2001 (along with .416 Rigby), so yes, you have a very rare piece. There are also some "uncatalogued" calibers floating around (7mm RUM, 300 RUM, 338 RUM, and 375 RUM for certain). I'm trying to figure out who the barrel maker was in that period; Krieger trued actions, installed & chambered barrels from September 2003 until the factory closed.

I see .416 Remingtons more often than other calibers, though I suspect that part of that is due to people holding on to .375 H&H African Expresses.