If you could look in the folders in that video the vast majority of their contents will look something like this.
The mailings sheet may not be in there.
All staff members are required to write letters to people in central files. At least that was the way it was when I was on staff. Let's say you have fifty staff members (dream on you lurking $cientologists) and fifty thousand or more central file folders. It can take a while before a staff member gets to a folder to write a letter. They're supposed to be hand written so the letter would be written with carbon paper and a copy made. The copy would go into the folder. Hubbard had policy and audio lectures on writing with reality to people in central files.
Most letters read something like this: I'll give a few examples.
I see you bought Dianetics.
What do you think about it?
(Yes, they'll use "ARC" on raw public.)
Write to me.
I care about you.
How are things going with you?
There is a letters out statistic and in $cientology quantity is more important than quality. For that reason most letters out are short and insipid.
When they do get a letter back from someone then the folder goes to a person on staff posted as a letter registrar. Their job is to develop that person and get them to buy something else. From exchanging communication with sea org letter registrars and seeing the turnover at the org where I was on staff I estimate the average life span of a letter registrar before being replaced is about three months tops. In other words they always end up being "downstat."