Not as rough as it looks - I believe it, that it actually looks worse in person. https://indianapolis.craigslist.org/cto/d/1976-buick-century-wagon/6605674697.html
She looks similar to a '73 Century I had years ago, with that same "sunbaked patina goodness". She looked a lot better with the "factory paint color goodness"! Pete
Happens all the time with rides down here - paint gets baked off. However, if that's the worst the rust is gonna get - I'll take it!
Seems to happen to all the GM Silver or light blue colors of the 70-80's. If the car is parked in partial sunshine it seems to make it worse, something to do with different expansion rates for a Panel part in and part out of the sun. The paint will just chip off all on its own.
Silver was especially vulnerable. I don't see rapid deterioration on modern silver-colored cars, though. I wonder what they did to the paint itself. Did you notice the rot at the bottom of the driver's door? Doesen't look typical for a desert car. Doesen't it. Maybe, it's just the drain holes being stuffed for so long
You are correct the drivers lower door does look like it is worse than the rest of the car, but it could just be the lower water seal hanging down, or it could be rotted out beyond salvage. On my 77 Century wagon I had to reseat the lower weather strip a couple of times a year. But it did have almost 300,000 miles on it when that issue started.
Amazingly, this junkyard refugee has not sold. But keep in mind, it really is not as bad as it looks! https://indianapolis.craigslist.org/cto/d/1976-buick-century-wagon/6832620481.html
Manufacturers were having a hard time with paint in the 70's. They were mandated by the feds to reduce VOC's (Volatile Organic Compounds) from oil-based paint systems, so there was a very long adjustment period getting used to the new base coat / clearcoat and water-based paints.
This jewel can still be yours. https://indianapolis.craigslist.org/cto/d/1976-buick-century-wagon/6860865166.html
Ya know. This is another Silver and red combo like that ‘77 Grand Prix. Great combo, the Grand Prix Just wears it better.