Do any of the forums Norma owners and users have an original 4x5 spring back? All I ever see is the 600KM international back in use or for sale. I am wondering if they discontinued it in favor of the flexible international back. The back I have is very light and compact with modest spring tension unlike the heavier hand of the international back. Inserting a film holder is a breeze and it sure lightens the camera in the field. I don't even see any mention of a spring back other than the 600KM in the Sinar construction unit manual. Dating it brings it to 1957-8 as original owner bought it then.