The signature structural rust point is the seal at the lower rear-window/trunk corner, which lets water into the trunk and rots the surrounding steel; savvy bidders repeatedly ask sellers to photograph up between the trunk hinges to inspect the metal around the rear glass frame. Compounding it, the rear glass seal is NLA from Mercedes.
Rust at the lower rear-window and trunk corner
Mercedes-Benz SEC Coupe (C126) · cosmetic