The lens was a rebranded Mamiya 14mm fisheye for the 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 Voigtlander VSL cameras with QBM mount. 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.
The original Mamiya version has Skylight (SL) – LB-A – Y48 (Y2) – R60 (R)
A metal variant of the lens appeared on eBay years ago, but I’m not sure it’s a real factory variant or some user’s custom rework. If you have any info please contact me.