Dom,
I did see that website about a week ago. Some of the catalog photo's appear to be right out William Green's Catalog. The listings aslo seem to be Green's
Williman Green made, published and sold a series drawnings of Civil War era Cannons dating back into the 1970's. I have a number of Greens drawing and in the early 80's made a number of cannons for resale using his drawings and techniques. I Currently have only two of those cannons.

You may recognize my 42 PDR above the Green called an M-1841. I think this is actually an 1840 pattern. Another part of Greens plans call this an M-1814.

There are other errors in the Green drawings, but you can still build a quite nice cannon using the Green drawings. I am waiting for some one to order a set of these drawings so we can see if they are based on Green's work. If they are they will be quite usefull.