The Zeiss Super Speed T1.3 PL Lens set are the most popular of all the vintage prime sets. They are seriously fast at T1.3 for incredible low light performance but are also light and compact. They are also very sharp above T2.8 but below that they give a soft look that directors love. One of the main reasons that vintage lenses have become so popular is that they offer a great solution to the problem of modern camera sensors being too sharp.
The most sought after of the Zeiss Super Speeds – the elusive MkIII. With the popularity and rarity of the Mk III Super Speeds, you’d think there’s some special, magical upgrade that makes them infinitely better than the Mk II… You’d be wrong. Similar to the previous enhancements, the ONLY upgrade from the Mk II to Mk III is the focus scale orientation. That’s right. The focus marks on the older Mk II are in-line with the lens body which means when you mount them to a camera, the focus marks are sideways. Zeiss took the advice of users around the world and updated the focus scales on the Mk III by increasing the font size and rotating the engravings 90° to orient the focus marks upright when the lens is mounted to the camera. In fact, this was something of a down-grade to some. Since the focus marks were larger and more legible, there was no more room for the dual-unit focus scale, meaning the lenses either came with a Metric OR Imperial scale, but not both. This final revision came about in the mid 90’s which enjoyed a relatively short production run.
For more information about Super Speed history: https://thecinelens.com/2016/08/24/whats-in-a-name-a-guide-to-zeiss-super-speeds/