Dear

Call it nostalgia, if you wish, but as I was glancing
over some of the accounts we have had for several years,
I stopped when I arrived at the name of (name of firm)

It has been a long time since our very first transaction
was initiated and it is with a great sense of pride that
I realize how far both of our firms have come since that
day so many years ago. The fact that our relationship
has not only lasted, but has flourished over this period
of time, is most rewarding.

Thank you for the past, for the present, and may the
future be a continuance of that which was established
on (date)