If it covers 8x10 I don't think it can be a tesser. Can it? Lets say the image circle is 350mm then that's an angle of coverage equal to 80degrees.

I did a search and the only real info I could find was they seem prone to separation and it might be a graphic arts lens. I found a picture of a 400mm version and it looked like a barrel lens somebody had mounted. Well it did to me.


They tried testing a 90mm version and it was separting.

OTOH it seems the people that used them mostly liked them.

BTW since you're holding the lens you're in the best postion to tell us the image circle-))