I looked at the links and waited to see if anyone else commented.

At first I thought it was one of the rechamnbered Kodiaks rechambered from .45/70 to .450 NE. One or two of these were done by private persons, and later resold. One was sold to the PH the client hunted with. They probably will appear on the market from time to time. If they do, is their a reason they are resold? I would make sure the rechambered barrels still regulate adequately after the changes. I can't comment on pressure etc as I don't know much about that. But that should be considered - ie is the change safe. Not comment pro or con, but get that answered to your satisfaction.

Pedersoli doesn't list a .450 NE in their line up so they are not standard.

The rifle in the picture/link has a different finish on the barrels and the comments seem to indicate the rifle(s) are made from the Pedersoli Kodiak. Perhapes .45/70 barrels rechambered? Perhaps re-regulated? Perhaps new barrels fitted to the Kodiak receiver? Something to find out.