It may be that gold pickups have an under-plating of nickel (so that the gold plating will adhere), but that is based on something a local plating shop told me about re-doing gold guitar parts a long time ago on a Gibson L5 tailpiece.
I'm not sure Guild ever really had any nickel hardware, aside from tuners from outside manufacturers. Strap buttons, maybe, but the tailpieces were all chrome and all the small and large humbuckers I've ever seen have been chrome, too.