I don't think the authenticity of the inscription on the box matters one iota. The Catholic doctrine like that of the Eastern Orthodox is the eternal virginity of Mary. This doctrine isn't upset if James was Jesus's step-brother or his cousin. The absurdity of this all is that somehow the inscription is proof that James is the son of the Virgin Mary. I don't find any claim in Scripture that James was this Mary's son. If Mary was present at the tomb wouldn't the evangelist have pointed that out instead of pointing out that she was the mother of James, but perhaps that's something the evangelist wouldn't claim because it was commonly held knowledge. What really gets me is that after 1500 years of the church we have these arrogant upstarts who somehow claim they have canonical proof of that the Virgin Mary is James's mother. When the reason that we have the Canon is because of the church.
It's not even a matter of 1500 years.
All the Reformers - Luther, Calvin, Melancthon, Knox, Zwingli, Bucer, Chemnitz, etc. believed in Mary's perpetual virginity.
The vogue for denying Mary's virginity really dates from 1854, when Bl. Pope Pius IX proclaimed the immaculate conception.
Since that time it's become increasingly popular among many Reformed Christians to deny Mary's perpetual virginity.
I don't think the authenticity of the inscription on the box matters one iota. Oh yea! This was a thread about a bonebox with some inscription on it. I remember now. Polycarp posted it a couple of days ago. How did I end up here...
Anyway, I'm in toal agreement!