Maybe you're talking about the viewfinder coverage of the Yashica. I've read something about that on this thread on Photo.net:
Originally Posted by temps variable
"Exposed negative size: 56.1mm tall by 56.9mm wide, width of exposed negative outside viewfinder field of view at 3.2m: 4.5mm top, 4.1mm left side (photographer's left, facing subject), 4.1mm right side, 2.1mm bottom. This is about 86% coverage left to right, 88% coverage top to bottom, 76% of total area. The view finder's field of view at 3.2m is 203cm tall x 198cm wide."