What is this Accessory on Toyo View 4x5?

]I searched this site and found quite a few links, but nothing that really answers what this is used for. A set of swing-away bellows in front of the lens. Just a lens Shade? maybe someone can help. I acquired this camera from a work mate and new to large format, but motivated. Someone directed me to Apug today, seems like my kind of place. I work in a custom photo lab.

Here are some pics for help on my question thank you.

It's what is known as a compendium lens shade. You can adjust it such that you eliminate any vignetting.

Yes, it's a compendium shade. If your groundglass has cut corners, sight through each corner after you've set up the photograph and focused and adjust the shade so that it's just outside the field of view in each corner, so that it will restrict the image to the minimum necessary, reducing lens flare and bellows flare, but won't vignette. It might also accept 4" square filters on the back standard and possibly masks on the front standard.

Ahhh! Thanks so much. I think I would have probably figured it out at some point through trail and error, but I haven't been able to afford the lens as of yet. I'm moving from 35mm SLR direct to 4x5. I've always been in love with a 4x5 positive image while processing. Can't wait to pull some of my own. Lenses are insane by the way. I'm hoping to come across a deal as I did with the tripod (Bogen 3051 with a 3063 head for $125, sold the 3063 head for $85 and found a used 3047 head for $25). At some point I am going to have to spend some real money on something for this hobby, it may as well be the glass. It's just hard waiting.

Thanks for the info.