As Paul has said, with most of the SLR cameras where you still could do some of the work yourself (other than just aiming it and pressing the shutter release button), the lens focal length that seems to produce a true 1:1 viewing image with true perspective as you see with your eye, seems to be right at about 58mm. Many of the major SLR camera manufacturers back in the early and middle 1960s made available a 58mm lens as one of their premium and professional offerings. There must be some reason why they departed from the "normal" 35mm film focal length for a "standard" lens of only 50mm.
And, I can add both Nikon and Minolta to the list of manufacturers Paul provided. Minolta was still offering a 58mm focal length lens at least into the late 1970s.