This is a pretty interesting article about the Martin D-45, specifically pre-war D-45's. There's also some commentary about the D-28 of the same period. http://www.premierguitar.com/articles/20677-pre-war-perfection-the-martin-d-45?page=1

And this is about some misbehaving little boys in Texas building counterfeit Martins and ripping off the good citizens of the pawn shop world, http://www.lehighvalleylive.com/nazareth/index.ssf/2014/04/cf_martin_and_co_counterfeitin.html

Martin uses a 'botanical' mark that, through DNA testing, can be used to identify counterfeit guitars. Guess it's only worthwhile after the crime has been committed...