Definitely custom as far as F1s go - it may be an off the shelf wheel from many of the wheel distributors in Japan that was simply forged as a blank and then the hub area was machined to match the F1. There are plenty of companies in that part of the world who could do something like that and the Japanese commonly mod their supercars in more unique ways than you see in many other parts of the world.
>8^)
ER