I have no doubt the books are bogus, but not on that point. He has sold five that are still shown on eBay as recent sales:
From the color and style I can see they are the WALTER J. BLACK set which was produced in the 1960s and are very common, often selling for a buck or so a throw. They are undated on the title page, but show the original and renewal copyright dates the next page over which confuses many. Certainly, they would not be around when Col. Potter was reading them in the early 50s. Early editions of Grey's work would have colorful, pulp type dust jackets. The question arises, that if all the books are identical, except for title, why would FOX need to use five or more?
20th Century Fox props are well distributed, so we know they had a particular inventory system for their property in order to keep it where pieces could be found quickly in their vast warehouses. The only markings in these books is the name ink written on the inside cover, a foil label with a random number and someone writing "Potter Tent #1" and in the others #2,#3, or so forth. Would any studio label an item this way? I doubt it.
There is/was such a Charity:
True, it is unregistered, but the address used is the office of the attorney.
More damning, however, is that I have been doing this longer than most of us and I never heard of AI PROPS AND COSTUME or the Hennington person, nor could I find any information on him. At the time of this sale, Alan Adler was the head of FOX Archives as anyone with a TITANTIC prop can read on their COA. I did find through the Social Security Database that only one person named Lucas Sollis is recorded to have lived in this country and he died in Santa Cruz, CA in 1966. Also, the LA TIMES archives produced no articles on the 17th or 18th of January 1999 editions about any such sale. Charities tend to advertise or get free plugs for their to-dos.
The good news, to me, is that you paid very little for them, so I hope it is a lesson learned. All the information you required to do your own research was in the listing and could be read on the COA.
rick