I think I have that piece. If you look at the A-S catalog you'll see the leather bellows, but it also uses 161013 and 161012:
View attachment 391806
I don't know what it looks like or how it is used without the binoculars. It came with a 6x9 F-Classic I bought some years ago. I tried it, but didn't really like it. My main issue is the magnification isn't very high. I have the same issue with the Sinar bellows magnification hood. I use a 4x loupe but I think this is closer to 2x. Aside from my issue with magnification the other reason I don't like it is it essentially requires that I remove it to insert the film holder (unless I was using it incorrectly.)
For size the biggest potential issue is that 161013 has a flexible "rubber" perimeter that seals it to your face when in use. If you fold it down too tight and compress that rubber you could deform or crease it.