I believe Prof. King thinks the text was originally written in Greek and later translated into Coptic. If the author was a Gnostic living in Egypt in the second century, he or she might have imitated other Gnostic texts so having similarities to other Gnostic writings would not necessarily show that it is a modern forgery.
Would there be a way to determine the age of the ink without destroying the papyrus?
If the author was a Gnostic living in Egypt in the second century, he or she might have imitated other Gnostic texts so having similarities to other Gnostic writings would not necessarily show that it is a modern forgery. Watson shows that the compiler had limited command of Coptic and relied almost certainly on documents later than 2c. But the larger point, made by both King and Watson, is indeed that people motivated to portray Jesus as a married man existed in antiquity, as they exist today.
I read in the article that first appeared about Mrs. King's discovery, that chemical analysis would not be possible.