[ThomasL]

I would suggest reading the thread about this same topic from 2015 for those who have not as some of this is explained there by folks better at it and more experienced than I

The case for its all written by the same hand - Written at same time with same instrument I believe was a big part of it.
T
Someone asked about other Jackson signatures from 1911 on documents...as for as I know there arent any, but Mike Nola is who needs to be asked that he probably knows. (there are some alleged on baseballs and they all look like the small scratchy shaky signatures that are on every thing else he signed)

This 1911 photo if signed by Jackson would mean that he basically just learned to write and wrote better at the beginning (presuming he learned after being married to Katie who taught him) than he would just 4 years later

Some are double posts but here are some signatures 1915-1921 and a 1945 drivers license