Leopold Beaudet determined the position using the plate proofs at Library and Archives Canada. He compared his measurements of known positions and none matched this example. As he stated in an email, “This leaves just one possibility, plate 66. The guide arrows on this plate were engraved after the proof was made, and no example of a guide arrow in the bottom margin has been attributed to plate 66. Thus, by process of elimination, your new example [illustrated here] must come from plate 66.”