Rolleiflex 2.8F/FX: Filters on both lenses? (Possible!)

I know that generally you can't put filters on both the taking and view lenses simultaneously, but then I stumbled across this. That appears to be a BW 40.5 UV filter on a step up/down ring to Bay III. Does anyone know what that stepping ring is to permit both filters to be on simultaneously? I have a FX I wish to protect dearly!

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A friend of mine has UV filters on both of his Rolleiflex T lenses. When I asked him why he said that although only the taking lens needs the filter, when the filter is on the lens he could not put the lens cap on them.

It could also be using filters to protect the lenses when no lens cap is available.

I am not actually positive because I've only used Rollei Bay style filters (which definitely will not mount on both lenses at once), but I think this must be using two Bay III to 43mm rings. 43mm is the smallest I have seen stepping rings from Bay III, so I've always assumed this is the cut off before vignetting would occur.

If you search around you'll find discussions of people getting Korean made recessed filters on the auction site. It sounds like these will allow mounting on the viewing lens while a hood/filter is on the taking lens, but I haven't been able to actually find them myself. I don't usually use filters on the taking lens, just a hood- it manages to deflect most potential damage from both lenses.

FWIW, it doesn't look like the set-up in that picture would also allow for a hood- at least not a Bay III style one; I guess a screw in could work on top of the taking filter.