Maybe Bauckham is being accurately represented in the footnote (I'd prefer to hear from Bauckham himself that he agrees with the interpretation of the inscription), but he is not an epigrapher. Christopher Rollston, who is an epigrapher who specializes in ancient Levantine inscriptions (and who was the epigraphic consultant for the National Geographic/Discovery Channel program on the find), believes that the initial letter is not an iota at all (http://asorblog.org/?p=1642), and if the letter is not an iota, then there is no tetragrammaton. The iota was written as a single vertical stroke in inscriptions of the period, not with a long horizontal stroke at the top as seen in the photo (the lower horizontal stroke is not even clearly visible). Maybe Bauckham was referring to stylized serifs used in elegant ornamental inscriptions, but what reason is there for expecting serifs to be used in ossuary inscriptions which were usually quite crude in style? And this is not a serif but a long, and deep, horizontal stroke, as Rollston states: "I must stress that the convergence of the cumulative evidence demonstrates in a cogent manner that the first letter is simply not an iota. In reality, this letter is most readily understood as a tau (i.e., a top horizontal and a vertical) or (alternatively) a zeta. However, it is certainly not an iota." If the iota identification is epigraphically viable, there ought to be other examples of the morphology seen in the Talpiyot B tomb in inscriptions of the period. It would be good to hear other epigraphers weigh in.
Rollston also notes on his blog that, accepting that the letter in question is a tau, the last two letters of line 1 and the first two letters of line 2 spell the word osta "bones" (pl.), which according to Rollston occurs in other ossuary inscriptions and burial texts, for obvious reasons.
And also Jacobovici makes a point that should imo make the tetragrammaton interpretation highly problematic (from Rollston's blog): "Jews did not – and do not – write the Tetragrammaton on a bone box filled with 'tumah' or impurity". That's a really good point. This makes a good deal of sense, but for Jacobovici this just indicates that there must be something super super special about this tomb that would allow such an unusual thing to happen. Whereas I think the more justified response is...hmmm maybe this isn't a tetragrammaton, the inscription isn't entirely legible anyway, maybe we should reevaluate our reading of the text in light of its intrinsic improbability. But this improbability is hand-waved away simply by the (already-held) speculation that the tomb must be Christian and associated with Jesus. This then is imo a circular argument since one must already accept this speculative identification of the tomb in evaluating the evidence.
