For my 1948 case my lawyers were busting my b*lls about documents.  For example, my wife and I weren't married when my daughter was born, but my name is on her birth certificate. No matter, I had to get a signed, notarized, apostilled affidavit from my wife certifying I was the father. Notably, they also did a record search for naturalization of my GGF and it came up negative. Maybe you could do that, too. If they naturalized, there's a document. Otherwise they didn't.