I'm sure all the letters are the same except for the date and name they put down on it
Exactly. That is confirmed. They are all the same. It is even the same letter they use in other countries. Same text. Standard letters have a number and code (sometimes not printed on it), they are ALL standard. Another date, another name. Thats it. Off it goes. Another poor bastard on the road...
Service Department works with lots and lots of standard-out-of-the-box-letters. It is too risky to have some secretary at the service department adding his own stuff and make the Society liable.
Trojan.