The 1987 550 line-up came in Road Flare, Desert Yellow, White, and Black. Black was the only one which came with a rosewood board. All RG5xx guitars were made in Japan.
I would guess you have a 1987, I'm almost certain on this, and the serial sticker has been removed or destroyed somehow.
If the vol knob is getting in your way fitting a new pickguard is easy. Any
custom pickguard should have the newer control layout with the repositioned vol knob, I'd imagine.