According to a report by Myce.com, Android 4.3 versions JWR66D and JWR53F have been spotted running on Nexus 4 and Nexus 7 devices.
If you break down the build number (JWR66D and JWR53F), this is what they say:
- ‘J’ means that they are Jellybean build from the second quarter of this year.
- ‘R’ and the number is the x-th day in the quarter, in this case 66th and 53rd.
- The final character remarks the build of the day, ‘D’ is the fourth build, and ‘F’ is the sixth build of that day.
- ‘W’ identifies the code branch that the Android is being built from.
Myce found traces of these new Android 4.3 builds by monitoring the user agent strings, which is used by browsers to identify themselves. Thanks to their tracking abilities, they found the following strings with the devices they were running on respectively: JWR66D- Nexus 7 and JWR53F- Nexus 4.