Hi everyone, I’m new to Hasselblad cameras. I’ve got recently a 500cm body with a kinda strange back. The back has indicator 16 on the side where the crank is and also there is letter M. What’s interesting that the 645 frame is not centred according to the square frame of a back. Unfortunately I’ve already loaded the film in the camera and took few shots, so I can’t open the back and take a picture and tell the position of the 645 frame according to a square frame, but I drew two possible variations. My question is if I want to make a paper mask on the viewfinder for this 645 back, where should be the wide strip of the paper in the viewfinder, at the top or at the bottom?