Correspondence from famed cartoonist Paul Terry

I found this letter tucked into a book that was published in 1915.

It seemed  like a great coincidence that the name "Terry" is written in a few places on the letter and that there are hand drawn cartoons on the letter and that it wouldn't be from one famed Terry cartoonist brother to the other.

I've been trying to figure out how to authenticate it and then to see where I could sell it.  I've been searching to find out if either of the brothers took a train trip to Cairo in 1902 without any luck thus far.

Any help would be greatly appreciated!