G'day,
authentificating historic pieces is a bit tricky, because a dial alone doesn´t make a piece a genuine Lange watch. And dials can be changed or reprinted; given Lange mostly used swiss movements for their historic wrist watches then, it´s quite difficult to determine what´s right and what not.
This even more so in the light of popular auctions, particularly internet auctions, where not every piece actually is what it claims to be.
To be sure, i´d recommend to send it in to Lange for a personal inspection and authentification; not just you´re sure afterwards, but in case it´s an authentic piece you may receive a certificate for it as well.
Greetings from Germany,
Peter