A #8B Faber-Castell 9000 pencil does a good job of
making notes on the back of RC B&W prints. I like to
jot down exposure data when I make a print so I can
make some sense of the printing session on the next
day when examining the dried prints.

I had been using a Sharpie marker but never liked it.
Used on FB paper the marker can bleed through, so I have
to keep a pencil handy in any case.

The pencil makes nice light marks that stay on and don't
smear. And it just 'feels better' than a marker.

Additionally the pencil won't mark the front of RC paper
so I get confirmation that I am not about to print on the wrong
side of the paper.

Available at art supply stores and via Amazon. Around
$0.80 each.

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation
http://www.nolindan.com/da/index.htm
n o lindan at ix dot netcom dot com