Here is a set authenticated (SGC) as entirely in the hand of George. I believe that it was discussed in a previous post and that this was also the opinion here.
Any dissident opinion? What is the value of an LOA from SGC? I am not familiar with them.
Based on my (limited) knowledge, I would say that your example could date from end 1962-early 1963 (before March), while the one I submitted could have been signed (as regards the different sig of George) after mid-1963.
The way he signed John Lennon here is very similar to the John Lennon autograph in the hand of George Harrison that I have (bought it from Tracks UK a few years ago). Here it is: