[Maursault]

The original image was, of course, a photograph made from negative B&W film. For one color printing, the picture was halftoned[1] to simulate greyscale or continuous tone. When the reproduced halftone image was scanned, due to the scanning dpi, it created a moiré pattern.[2]

[1] https://en.wikipedia.org/wiki/Halftone

[2] https://en.wikipedia.org/wiki/Moiré_pattern