The Unknown deed doesn't seem to be super-rare. From what I understand, they were easy to make for people who knew how to do it--something about using UO Assist's Make Last Item macro to create some object that no longer existed. I think it might be worth around 250k, but prices seem to vary a lot.
I think the white 1gp check might be worth 2 or 3 million, since it's pretty old and 1gp is a very popular amount.
These are just ballpark estimates and may be out of date.