I believe that to find the truth in a work of art it must be observed in a manner that is unnatural for most of us. Never gather an impression from the whole- examine the part. First above all look at the qualities of the engraving- this is the most telling part. A great artists work flows and moves like the line from a brush-effortlessly. This is the foundation upon which all else is built. If said foundation is solid all else will stand. On the matter of authorship- all objects viewed without the encumberances of prejudice, preconception, expectation- will tell all. A work produced in 1750 does not look like one made in 1850. No matter how hard the latter persists in its attempt at deception it will fail.
-StevenK