The Berliner Motor Corp went out of business in 1984, they were headquarted in Hasbrouck Heights, NJ; I doubt that the records are still in existance, never mind accessible; US law requires only a 7 year record retention. If the records do/did exist they would be able to tell you what dealership your Norton was delivered to and who the initial purchaser was, the trail could end there. And, don't forget, computerization of vehicle records didn't really catch on until the mid 70's in progressive states, mid-late 80s in backwater states, your Norton records have little chance of surfacing cohesively.
Having just purchased a 1972 Norton with no geneology I have found that, even complete machines, may have been through scores of owners. I have also found that very few states in the US require a title or title search for motor vehicles older than 15 years. The key to your success is finding out how high a level your motor department needs to see documentation from to endorse your ownership; I have the same problem in MA with my 1972.
Here is my plan: I will sell my '72 to my daughter in Maine that does not require a title for machines older than 15 years, she will take the notorized bill of sale that I provide and get an insurance certificate then pay the states's excice tax then on to the DVM for plate and registration. A short time later she will cancel the registration, end the insurance and "sell" me back the Norton. At that point I will have a notorized bill of sale, an original Maine state registration certificate, endoresed to me and Massachusetts will take all that in an issue me a title, pure bull shit but it satisfies the games' rules...
You can get a US title in a number of similar ways; there are several title companies (in the US) that for a $250/$350 fee will, essentially, do the same thing. If your motor vehicle department will countenance a US title this is your out.
I wish you good luck.
RS