The seller is an honorable chap. My Canon IIb with matching Serenar 5cm f/1.9 LTM was from him. Beautiful!
As for the 5.8cm f/1.5 and the common associated 6cm f/1.5 Sonnar lens, it's often debated.
We know for sure that Leica does not use the Sonnar optical design and hence will not mark the lens as such. So the "Leica" Sonnar 5.8cm f/1.5 lens should be avoided if you are particular about authenticity. It is also marked "Sonnarex" on some lenses. Incidentally, the lens on auction carries a "V" marking instead of "T" marking.
The use of aluminum parts on the barrel/mount is often indicative of eastern european origins, where many other bogus offerings also originates. A search on fake 5cm sonnar makes an interesting read for those interested.
In addition, Marc James Small, a respected author on LTM copies/replicas, cannot ascertain that Carl Zeiss Jenna did in fact produce the 5.8cm and 6cm Sonnar lenses. He retracted his earlier assumption that these lenses were of CZJ origins and indicated that the factory records cannot give evidence to their existence at all.
It is speculated that these odd ball lenses could have been hand built by skilled technicians in the Eastern Bloc to raise hard currency. Hence it's not impossible for some of these lenses originally meant for the M42, Exakta or Praktina mounts to be 're-presented' in the LTM format. And the nature of their underground operations could be the reason for the absence of a brand/origin marking.
Here's a Japanese page that shows the 5.8cm f/1.5 lens side by side with the 5cm f/1.5 lens.
If you just want to play with a vintage odd ball (Sonnar!) lens, by all means go for it! You might just find an optical treasure. Collectors should obviously stay far away from this one base on the (lack of) information available.
Hope the information is helpful.
Cheers,
