I see it aswell, he's talking about the faint extra line surrounding the nose. Not entirely for sure, because I've been off for some time and am rusty, but I believe it's just Machine Doubling, nothing to get too excited about.
Life is like a box of chocolates, you never know what your going to get - Forrest Gump
PART IV. Die Errors: Die retouching (master hub, master die, working hub or working die) Retouched details on master and working hubs (1920s to 1940s) Retouching Of Design Elements http://www.error-ref.com/?s=trough
Quote: The term "channeling" is used when referring to retouching efforts that produce a thin trough at the margin of affected design elements.