This image is related to Schaaf number 4668, Schaaf number 4678, and Schaaf number 4679.
To create this image Henneman has created a new single calotype negative that contains two photographic images from "The Annals of the Artists of Spain" (1847). This is probably an ingenious attempt to save paper, as well as time and money. By producing single negatives that contain more than one image, Henneman was able to print two plates for the finished publication in the time it would normally take to print one. He has doubled his productivity rate, or halved the time it takes to produce a plate.
For more information on "The Annals of the Artists of Spain", see the project blog by Hilary Macartney.