My Mother was a Legal Secretary for a Lawyer for 20 years (1922 to 1942), and we had two Underwood manual typewriters at home.
She was a Twin and they would type a letter to each other every day. As a young boy, my mom encouraged me to start using the typewriter at a very early age. She would say, 'come here Joe, and type a few lines to Aunt Ruby".
So, I would sit down and write "Hi Aunt Ruby. How are you. Today, I played with my friends. Well, that's all for now. Love you, Joe"
I was 6 or 7 when I first started typing these little notes to my Aunt. A few years later, my Mom started teaching me Typing out of a old book called "Rational Typewriting - Revised Edition.
I still have the book - She bought the book in 1921. I also have the old Underwood Typewriters.
Joe