There are a couple possibilities that would give similar results.
One is carbon printing that can create an image that has a raised relief -- a very permanent image is created using gelatin and pigments of your choice...and transfered onto a final support (paper, glass, metal). The blacks are made of a thicker layer of gelatin than the whites. This is the process I use.
Then one could use the same process, or with photo-sensitive polymers to create a raised relief that can then be pressed paper or metal -- or used to create a mold to pour the plaster onto to create the relief in plaster.
I believe the Hybrid forum has a discussion on the polymers.