While I wouldn't stand up and say that's definitely koa, the pics are all on the dark side and the grain does look sort of koa like. I think it would take a more accurate picture or a wood card to tell the tale. Koa neck stringers would be pretty unusual, but who knows what sort of experiments they were doing with wood types back in '87.
In any case, at $8K for a signature instrument, it almost wouldn't matter what the woods were in terms of value.