Originally Posted by B-9
John, it is indeed a square Copal shutter. I would have to say the design has really proven itself over these 53 years!
Actually, the Nikkormats (FT, FS, FTn) used a "Copal Square II" shutter which was a refined and much more reliable updated shutter. The original "Copal Square" was less reliable and appeared on only a very few cameras. The Nikkorex F and its Ricoh near-twin (Singlex F, I believe) used the original version, which is identifiable by being clearly marked "Copal Square" on the shutter blades.