I realize that this post and string is a few years old now but I just stumbled upon it and thought I would contribute what I could. I have this same exact picture. It is printed on heavy card stock, almost like a post card but mine is in very good condition being as it has been kept in a 5x7 frame for the last 50 years. Let me give you a bit of the back story as to how I got mine.
I have cousins who live in Liverpool England (and still do as far as I know). My grandparents were very close with them and used to go visit every couple of years. In early 1964 I was 6 years old and absolutely a huge Beatles fan already. I absolutely loved them. When I found out my grandparents were going over to England for a visit, in my youthful innocence I asked if they could get me their autographs (as if it were that easy). As it turned out my relatives there lived only a couple of blocks from where Ringo's mother lived. Not wanting to disappoint their American cousin They took my grandparents over to the house and knocked on her door to see what they might be able to get for me. There is more to this part of the story but the short version is that Ringo's mom invited them in and after some conversation gave them this card to give to me.
What I am about to tell you is the explanation that Mrs. Starkey gave to my grandparents about what this photo actually is. This photo was a promotional piece the boys had printed up in limited quantities to give to the parents (or other family members) for just such an occasion. This is why yours is signed by Mrs. Harrison, Georges mother. They were only given to family members
. It was intended to be a hand out, to give to, and hopefully satisfy, fans who might come around looking for a "piece of something" from their favorite Beatle, to keep them from tearing off shingles or shutters or doormats or whatever, to have a piece of Beatles memorabilia. This story was verified and discussed many times throughout my life with my grandparents, so it is a first hand account, and I have every reason to believe it is true.
Furthermore, While it is true that Brian Epstein (their manager) or Mal Evans (longtime friend) would frequently sign promos for the boys I have spent many years researching the signatures and have found them to be authentic. Not original, they did not sign every photo, they are reproduced, but authentic. Unfortunately mine does not have a signature on the back as yours does.
If you read this, I hope it helps you. In closing, being as you are not a Beatles fan (and I still am
), I would be happy to take it off your hands to have as a companion piece to mine.