My theory
I have run across two GNX's where the owner had two "original" window stickers. In both cases, one was a "Buick" GN style sticker clearly listing the car as a GNX with the GNX number indicated, the other an ASC McLaren version that we're all familiar with. My theory is that the cars were delivered to ASC with the Buick sticker displayed on the window and during the GNX modification the Buick sticker was removed and replaced by the ASC version. Perhaps some of the original removed buick stickers were left in the cars, stashed in the glove compartment or under the seat,etc. As a side note, I have the original quality control ASC internal audit checklist for my GNX. I have no idea how the original owner came by this document, unless it was left in the car in a similar manner.