The right-side quarter-panel was sanded properly and ready for a coat of metal glaze, also referred to as finishing putty. It's like body filler, but lighter and thinner, and used as a "topcoat" over body filler. It's easier to sand and therefore more useful in final-sanding surfaces with compound curves or complex shapes. It's also less porous than body filler and shows fewer pinholes when painted over. notice the light green color of the glaze on the taillight panel.