Wow that is a good price
That side burner looks exactly like the one that was on the 2000-01 Genesis Gold I picked up so I'd say original to that series grill.
Seller calls it semi custom. It does look like a shallow 5-bar firebox, so that could be from a Silver A. Is this what Jon Tofte wants to put together?
Where are the flavorizer bars???
Edit: Were the two burner Skylines essentially a Spirit with the Skyline hood? I didn't realize that the Spirits of that era were 5 bar boxes. I was under the mistaken impression that the 5 bar boxes started with the Silver/Gold/Platinum series grills.