The so-called opera windows (oval shape) or portholes (round shape) were a popular dealer add-on in the mid-70s. It all started with the '72 Lincoln Continental Mark IV which offered opera windows in the C-pillar as an option. They were so popular on the Mark that they were made standard in 1973. Pretty soon knock-offs were showing up on everything. I've got to say though, I've never seen them on an E-body. Any pictures?