Words from the owner :

This wide angle aspheron adapter was made in Switzerland and is incredibly rare. I snagged this as I was first building my super speed set but have over collected a bit and this and some other s16 lenses have to go. It’s definitely the cheapest way to get the really wide end of your lens set while staying in the Zeiss Superspeed look, because you are truly using the same lens. You’re also getting a faster stop than I think any of the other extreme wide angles below 6mm offer because this only works on the s16 Zeiss 9.5mm Mk I and the s16 Zeiss 12mm Mk I. The adapter included with the aspheron only fits those two lenses. You might be able to manufacture it to work with something else, but it was specifically designed for those.
Condition is fantastic. You can see some wear here on the exterior paint from use, but the lens itself is flawless. The metal caps it came with are great for keeping it protected. I recently did an interview series where I used a 9.5mm with the aspheron for the ultra wide interview angle and I’m happy to share those frames if requested.