What Scott said! The 360 has been discussed a lot on the Large Format Photography Forum over the years, it's worth a visit. In short, some people say it covers, some say it doesn't. I've never seen any manufacturer info on this particular focal length, though I do have copies of datasheets on some of the Computars in shorter focal lengths.
I have Computars and Kowa-Graphics in other focal lengths, as well as a KG360, and based on the patterns of internal reflections the 360 differs significantly in construction compared to the others (which all have reflection patterns that are basically the same). Given this, it may not be valid to make assumptions about the 360's coverage just because it shares the Graphic Kowa name. I have mounted my personal 360 Graphic Kowa on an 11x14 camera; it illuminated and appeared sharp all the way to the corners based upon what I saw on the groundglass, but I never made an image to see just how sharp it truly was. I wouldn't know where to find a 12x20 locally on which to try it.
Keep in mind that someone else's definition of "covers" may not match yours. Especially on eBay.
Oh, and if you're using it for portraits or close-ups it'll exhibit more coverage than at infinity...
