There are now other more detailed stories emerging (along with some nice photos) in connection with the new find of Christian mosaic inscriptions in the Megiddo prison yard. Go to post no. 1 in this series and scroll down to the updates.
UPDATE: Also see the comments section of this post, where I address a reader’s questions regarding the so called nomina sacra (“sacred names”) abbreviations which do appear in one of the Megiddo inscriptions and which may have an impact on the question of dating.
Nov 16.: Jean Véronis now has a discussion (in French) on “sacred names”: Ecriture: La Nomina Sacra sous la prison.