Manufactured from 1961 to 1964. This model used the "S" type lenses like the Reflex S. The shutter release was moved to the front plate and the meter changed to a "sleeker" looking one. Frame counter was also moved to the base of camera.
On later production the cameras had a longer selenium cell and the setting button was moved to the back as on the Reflex IV model that followed.
Early production, this one with 50mm f/2.8 Xenar lens
Late production, this one with 50mm f/1.9 Xenon lens
Here is an amazing cut-away picture borrowed from Keith South's "Living Image Camera Museum" website.