Description: The IIIg was the final screwmount model. Introduced in 1957, three years after the M3, it was mainly produced between 1957 and 1960, although a handful were assembled up through 1966. Functionally, the difference between the IIIG and it's predecessor, the IIIF, is the viewfinder. The finder window is much larger than on earlier cameras, and contains bright frame lines that move as you focus to correct for parallax. The frame lines are illuminated through a small rectangular window next to the viewfinder. On the back is a film reminder dial similar to that of the M3.