Bayonet filters: Is B50 the same as Bay IV?

I saw a filter listed on Ebay as a Bay IV mount. Looking at the photos, the back of the filter says 'B50' not IV. I thought that B50 is a Hasselblad system. Which makes sense because the filter is Zeiss.

https://www.ebay.com/itm/296290623347 (link for reference only)

Lots of knowledge about assorted Hassy filters here- is B50 the same as Bay IV?

And just a side note- the filter is labeled Zeiss Ikon. I think of Ikon as related to folders and other Zeiss cameras, not Hasselblad. Any info on the way Zeiss called itself over the years, the use of 'Ikon' as a basic barnd, not just camera model specific name, or such, much appreciated.

Zeiss Ikon was the name used by the Zeiss Foundation for its photographic camera branch. During economic collapse in prewar Germany, Zeiss realized that almost none the multitude of German camera makers would survive to use Zeiss lenses unless the industry was consolidated and rationalized. So Ikon doesn’t refer to any particular camera type. The person credited with rationalizing and saving the German camera industry was Dr. Emanuel Goldberg.
The question might be: was there another camera that used similar filter.

Hi Dan. I've always thought that the Rollei Bay IV and the Hasselblad B50 were different proprietary mounts, but can't be certain as I've not had a camera with eitehr (only Bay I and B-60). Unless someone has definitive k nowledge, may I suggest that you send a question to Tim at filterfind.net... he surely knows. And if not him, then Hasselblad Historical.

The mounting lugs on your example, although marked Bay 50 are a lot narrower than any Rollei or Hasselblad filter I've ever seen.

While this doesn't appear to answer your question,,, have you seen this? I've never seen it before but your very intriquing quesiton brought it to my attention:

No the Bay IV and B50 are two different proprietary mounts. And the B60 is yet a different mount.

The Meopta B40 lens hood has two bayonet lugs opposite one another, just like that.
Used on the Flexaret VI onwards, iirc.