I've never heard of a production RG550 in Natural finish but I've seen a couple of ones that have been stripped of their finishes leaving the body natural wood colour with the
black pickguard.
Ibanez not only have the RG580, but they also used to produce the RG547 and RG548 both natural finish, ash bodied RG 570 style guitars. The 547 had gold hardware and the 548 had black.