Not that rare or exciting but interesting from a historical point of view, I think.
@Räuber might also be interested.
It's already pretty much established, that after the Americans first and then the Russians carted off all the gear and assembly tools, the Jena factory and the workers had to start again from scratch. This, of course, led to the mechanical (and likely optical) design of the 3 million post-war Jena lenses to be a radical departure from what the prewar and wartime (and Russian) designs were like.
So here is a lens that probably marks this transition from where they scavenged the few parts they still had while the production of new mounts and lenses spun up.

Very early 3million Serial. 3001483 External housing is that of a prewar chrome Sonnar. External housing is made from brass. The aperture ring is made from a lighter alloy and the machining of the aperture wing is less well defined than usual.

I brightened the image to make it visible. There is a red 'T' between the '5cm' and 'Carl', it however has been expunged. Scratched and then filled in with black paint. The lens is only partially coated with the middle triplet being fully coated and the rear triplet rear lens bearing remnants of coating. But not the aperture facing side!

Also the rear triplet housing bears the serial number x268716 making it prewar. It has some balsam separation, but the lens works and registers correctly to the Contax standard without me having done any work to it (I have since maintained it) which leads me to believe that this was likely "factory" and not someones repair since the chances of achieving the correct focal length of 52.4mm by swapping in a random rear triplet are very slim.

Lastly we can see that the aperture mechanism belongs to a war-time lens going to what I assume is f/22. However the aperture scale itself only goes to f/11 as customary for pre-war and very early war-time lenses.
The lens weighs 181grams, the rear element diameter is 24,21mm and the front clocks in at 34,55mm.
Edit: The other thing that makes me believe that this is factory work is the deleted red 'T'. If this had been an unscrupulous seller or faker, the red 'T' would have actually increased the lens value at the time, especially in 1946 when most amateurs would likely have never seen a coated lens before not knowing what it even looked like. So they would have just kept it - especially since the lens is - at least partially - coated. But I guess that's not enough for Zeiss to label it 'T'.
We see this in the 'SturzVisier' or 'Leica' Sonnars which are (well the LTM mount is, the glass is real) fakes, and some despite being uncoated bear a fraudulent 'T' which later was changed to a 'V'.