my view.
first, I dunno if this was THE brochure car. Certainly it was a model that actually got built that looks to be the model the marketers used in the copy. I have owned many such cars over the years.
second, my experience in the car biz (though 20 years after this Monaco was built) was due to lead time for ad campaigns/brochure production, the cars could change.
Heck, we (the makers inside the company) sometimes arranged to have NON-saleable (e.g., built on the pre-production line, but hadn't completed all their production validation steps) all prettied up but TOWED (i.e., they were illegal to drive on roads) to wherever the company marketers/ad agencies photographed them.
Dealers will tell you probably even today .. prospective buyers show up/inquire with marketing materials in hand to show the dealer, and then say 'I want that one." Maybe dealer had one ion the lot, maybe it had to be ordered, built, and delivered later.
We even at my OEM (I am sure others did too) we had to add some kinda of disclaimer language in marketing brochures -- "certain vehicle details and specifications contained in this brochure may differ in available models, yadda, yadda" - to avoid getting sued by dealers/customers (seriously - otherwise "false advertising").
So, back then the actual car in photo was NOT the exact car sold to the public.
We almost ALWAYS, however, went into productioin with colors/features/etc., we advertised as available in marketing materials done several months before SOP.
LSS - my opinion is the '69 Monaco 500 for sale is NOT the actual car photographed for the 1969 brochure. Rather it much more likely represents a built car that had the look/colors/features advertised available IN/ON the photographed/advertised brochure car.
I have no comment as whether anything I just said affects its value today .. seems to me there more relevant inherent factors that will decide its valuation today.