A new firmware build has been certified for the Xperia Z (C6606, C6616) with build version 10.4.C.0.793. Our guess is that this could be a specific carrier update for the T-Mobile Xperia Z or maybe another variant.
The latest firmware that is meant to be rolling out for the Xperia Z has build number 10.4.1.B.0.101, and this version has currently not made it onto the PTCRB website. The rollout of this firmware has been very limited so far, but we’ll let you know once it sees a wider launch.