Rolleiflex UV filter for TLR's with size bay III mount
The last UV filters for Rolleiflex TLR's from the factory were high-quality filters made from black anodized brass. My understanding is these were from Heliopan and it does appear to be multi-coated. It has another filter mount on the top face so that filters or other accessories can be stacked. The factory doesn't supply these and hasn't since 2015. These are quite hard to find.