Comparing the surface markings of the lower-left corners of the grayscale images of Back (I) and Back (II), we can see how background details and the signature are nearly the same between the two states, although it is also evident that Matisse dealt with the cast of a nail head in the first state, either chipping it off or covering it in a light layer of wet plaster. This confirms that he started his work on Back (II) from a plaster cast of the previous state.