If I were to sign it now, I'd be committing forgery. I'd be putting my 1943 signature on a canvas painted in 1922.
Pablo PicassoWe didn't want to sign the painting itself, that would have interfered with the composition. And even later, for that reason or for another, I sometimes marked my canvases on the back. If you don't see my signature and the date, madam, it's because the frame is hiding it.
Pablo Picasso