The lens was a rebranded Mamiya 14mm fisheye for the Voigtlander VSL with QBM mount, it was intended as a cheaper alternative for the 16mm Zeiss F-Distagon f/2.8, and it was also rebranded with different finish and look for the Rollei cameras. It was part of foolisg Rollei policy having a confusion of brands, names etc. It’s a full metal construction with aperture going from 3.5 to 16.
It spots a filter turret, the control is nicely built within the hood. I’d like to know which filters were available.