Felt-tip markers appeared in the 1950s under the name "Magic Marker" and
were not fine-pointed enough to write photo captions for a while after
that.
But in the 1890s one would have written on pictures using a dip pen and
India ink. India ink dries waterproof and was often used for outline
drawings to be painted over with watercolor. It also adheres to all sorts
of surfaces that won't take ordinary ink. It is very dark black, a bit
on the brownish side when diluted.
--
Michael A. Covington http://www.ai.uga.edu/faculty/covington/
Artificial Intelligence Center <><
The University of Georgia Unless specifically indicated, I am
Athens, GA 30602-7415 U.S.A. not speaking for the University.