I saw this at the WIZN transmitter site in Charlotte, VT:
Somebody went through quite a bit of trouble to chart the transmitter readings from April of 1987 through about February of 1992.
A closer view:
I have not seen this at any other transmitter site, so I though it was an interesting way to keep a transmitter log. It also seems to be time consuming and a bit obsessive. Over the years, I have found my fellow broadcast engineers to be a somewhat strange group sometimes.