The language of The Jehoash Inscription is fake. It is not idiomatic ancient Hebrew but rather a perversion of it. If authentic, it would be a phenomenal find. But clearly it is not a genuine artifact.
To be declared authentic, any inscription that has not been excavated under controlled conditions by professional archaeologists must pass three basic tests. One is physical: The stone, the patina and any markings must all be judged to be ancient by an archaeological laboratory.
Second, the shape and form of the letters must be appropriate to the time and place that the inscription is believed to hail from. This is the paleographical test.
Third, the language, rhetoric and form of the inscription must be those common to monumental royal inscriptions of the First Temple period (tenth through early sixth centuries B.C.E.). This is the philological test, the area of my expertise. Paleographers have already declared the inscription a forgery. Geologists are apparently divided. As an expert in the languageof the Hebrew Bible, I have no difficulty in declaring The Jehoash Inscription a fake. Colleagues with whom I have discussed the matter agree.