F = Fake

Having somehow been made aware of this sketch yesterday, I started thinking about forgery, especially art forgery, for this one appears so obviously to be one, since the style seems so much at odds with other da Vinci sketches and rather displays stylistic features of the 20th century, like the sharp outline. Yet it took decades to discard it as such.
About art forgery there is this theory that the fake items will for some reason always display features that are prominent for the era in which it actually was faked. Though in retrospective it becomes easy to discern these features, the experts at the time will hardly recognise them.
For some reasons I'm sympathetic to art forgery because I feel that it does not so much affect art itself but rather ridicules the art market.