I'm afraid the general consensus is this man is bogus, an imposter, fraudster, charlatan etc.... there are no JG 53 records relating to a pilot named Gottfried J Dulias and no reported claims for such named pilot found in the OKL Fighter Claims records. Jochen Prien cannot find any mention of this man in JG 53's records, nor do any former members of this squadron recall a pilot by this name. There is no record for Gottfried Dulias in any list of Luftwaffe aces with 5 confirmed victories. IMHO, enough evidence to convict.
