Assistance Requested in Figuring out the Abene B-600 Attachment Ring

I don't have one of the B-600 attachments but I am really curious to know exactly how it is built where it attaches to the mill.
These links provide photo and video of the piece.

It looks to me that there is a part that bolts to the mill with a threaded section. The B-600 has a threaded ring with spanner holes that threads onto the ring and secures it. Two dogs prevent rotation.
What I can't figure out is how they got the ring over the other part that also has the t-slot for the bolts that allow the B-600 to rotate. Refer to the video link below at 38 seconds to see the t-slots and the ring. At the end of the video is the threaded part on mill.

https://www.practicalmachinist.com/...o-mori-seiki-lathes/schaublin-13-head-235295/

Abene B-6 drilling and milling attachment - YouTube

On this page is a few more pictures which seem to show the spanner ring hanging at an angle which implies to me that it isn't threaded on and if it was how would it tighten up so I think it is shouldered. 6th and 7th images show the angle.
Abene VHF3 +B6?! • Maskinisten

This is my best guess but how would it be assembled. Please show me what I'm missing. Thanks.

There were two types of mounting rings for the B-600 head .
The first was an unthreaded ring on the spindle nose with a
flat rimmed collar on the head that advanced / threaded up against the ring on the spindle nose keeping the head stabalized along with the #40 taper . The second was the threaded collar type that you see in the film .
I think the one shown in the other photos is type #1 .
I have the type #2 but haven't looked at it in a while .
I have a blueprint that I'll dig up and report back .
Ted

Has anyone ever seen a picture of a B-600 mounted on an Abene (other than the sales literature)? If so please post.

Hi
It happens to own a B-600 that doesn't fit on machines with quill.
Do check some photos I have collect through the years from the net.
And a schematic of the head from ABENE.
best regards
Kyriakos

Thank you so much for the post and images.

Sorry , Dominus beat me to the drawing .
As you can see the threaded mount ring pushes against a row
of ball bearings #47 that are dropped in through a hole in the ring #46 .
So to mount you pull the #40 taper in with the draw bar then thread the mount ring on to the nose ring til a little better than snug .