Zeiss T 1.4 super speeds are NOT MK I. They originally came in “B” mount with no gears on the iris or focus.  They rotate from close focus to infinity in a 180 degree turn of the focus barrel and have markings in feet AND meters.  The front elements are different sizes and need to be modified with Delrin 80mm front spacer rings and Arri gears. If you want them in PL (Positive Lock) you can use a “B” to PL adapter or change the entire rear mount to PL. When you are finished modifying, you have the Frankenstein bastard child super speed lens set from Hell that nobody wants to rent or own. The optical quality is excellent.

The lens on the right has the after market PL mount and Delrin focus gear.

The Zeiss MK I super speeds in PL go from close focus to infinity in a 180 degree turn of the focus barrel and have markings in feet AND meters. Some early models had no Arri 32 pitch gears on the iris. The assistant cameramen found it hard to hit marks when pulling focus so Arri/Zeiss changed the next generation to 360 degrees of travel from close focus to infinity.
 

The Zeiss MK II super speeds in PL go from close focus to infinity in a 360 degree turn of the focus barrel and have markings in feet AND meters. This 360 degree movement is sometimes referred to as having extended markings or engravings. These lenses have factory gears on both the focus and iris.

 

Zeiss MK III super speeds in PL go from close focus to infinity in a 360 degree turn and have extended markings in feet OR meters. They also have much larger engravings then the previous models. These lenses have factory gears on the focus and iris.

 

Zeiss T 2.1 lenses are all in feet AND meters. The MK I models may or may not have the gears on the iris and focus. The MK II models have factory gears on both. Glass (picture quality) is excellent on most T 2.1 lenses.  The 12mm is the least sharp of all the T 2.1 lenses.
 

Zeiss Ultraprimes in PL go from close focus to infinity in a 360 degree turn and have extended markings in feet OR meters. They are slower than the speed at T 1.9.   large engravings . These lenses have factory gears on the focus and iris.  You would be hard pressed to notice any difference on the screen between these lenses and the previous models.

Zeiss Master primes in PL go from close focus to infinity in a 360 degree turn and have extended markings in feet OR meters. They also have large engravings . These lenses have factory gears on the focus and iris.  Outstanding quality.  Super expensive.

Glass (picture quality) is excellent on all T 1.4, T 1.3 and T 1.9 lenses.