I strongly believe this is legit, but I don't know the seller. I met a guy who owned this box about 10 years ago. I lived in Houston at the time (Spring actually), and the guy owned a billiard supply/table store on Stuebner Airline between the Beltway and Hwy. 1960, if any of you from Houston know where I am talking about.
The buy had previously worked at another billiard supply store in town in the 70s-80's, and they paid Willie Mosconi to come down to Houston to put on an exhibition. When he got there, apparently George was making a couple of shafts for him, and he found out that they were ready and had the shafts shipped to him in Houston. The box was simply placed in the attic of the billiard supply store, and stayed there unnoticed for many years until the owner wanted the attic cleaned out and all of the "junk" thrown away. The guy noticed the origin and names on the box and simply took it home instead of throw it away.
If this is the same box, I have held it in my hands and it is legitimate. I contacted Victor Stein or Paul Rubino (can't remember which one) at the time and he told me that he would give him $2000, and that was 10 years ago! Don't know if he remembers. It was around the time the first edition of the Blue Book came out.