Quote Originally Posted by jnanian View Post
in the days of autographic film, there was a trap door that opened
and the photographer used a stylus and wrote info in the door/spot
it was like carbon paper and transfered to the negative and appeared
as white letters on the print ..

you could so something similar and take a sheet of mylar / plastic
larger than the image and write your name on it and print through it onto the paper it will appear white on the print ...
The type of printing I'm thinking of was done at the time the print was made, but the lettering/printing was black. So, it may have just been some type of stencil that the photographer had made up. I thought I had read about some other device that could "burn" the photographer's name onto the paper, but I may have been mistaken.