I was told by a fellow collector that when he went through his second divorce in the mid 1990s he sent out pre-prints and possibly secretarial items but I have never yet seen one so don't know if it's true or a myth!
"Everyone who writes gets an answer, and I always tell them the truth. Phil reads through the letters and sometimes writes an amount next to them; it can add up to quite a few thousand by the end of a session."