Look at the body line on the rear quarter and compare it to the body line on the doors. You'll see the line is flat without the detail. This means a big patch panel or an Ebay panel was used for a rust repair. In the second pic, you'll see the panel doesn't curve and follow the body contour.
It's become a typical repair using what's available. I personally think it shows a lack of skill on the bodyman's part if it came from a pro shop, but I understand if it was done in the backyard.
Of course, we've had a car posted here with a similar repair that everyone was drooling over....