The fella that owns this car, 8R02S Marti build date 3/18/68, asked what is this line down the rear window ? My reply "I am sure I don't know but I might know where to ask" The line or etching in the fastback rear glass window, centered in the glass and etched from the top/roof to the bottom/trunk. Does it have a purpose or what was the intent ? Does the 67 have this feature as well. Is this a replacement window? I forgot to look for ID marking. Thanks, Brian