The first version of Super-Takumar 50/1.4 with 8 elements optical design.
Introduced with the original Spotmatic. Can't be used on earlier bodies due to the protruding rear element (earlier bodies could be modified by changing the original square aperture actuator to the curved type).

The earlier version can be recognized by the IR mark being inside "4" and the protruding rear element. Later 7 element version of the lens has IR mark between "8" and "4".
The protruding rear element of the earlier version extends outside its metal holder (about 0.5 mm and due to curvature even more).
The newer, 1966-1971 versions, has its rear element entirely inside the metal casing, though both lenses extend the rear noticeably outside the body when focused to infinity.

Takumar 50/1.4 versions:
Asahi Optical Co. Super-Takumar 50mm f/1.4-16 (v1) 8 elements (this page)
Asahi Optical Co. Super-Takumar 50mm f/1.4-16 (v2) 7 elements
Asahi Optical Co. Super-Multi-Coated-Takumar 50mm f/1.4-16
Asahi Optical Co. SMC Takumar 50mm f/1.4-16