This is probably the longest period of testing for the maintenance update build for Mac OS, and today, Apple seeded its 10th beta to the developers. The new build does not have any feature change, but has squashed an important bug which would crash any application for using a small command. The new build, 12D61, is also expected to be the final build, considering the number of bugs and also the time taken to develop this update.
The 10th Beta has no known issues, and again, Apple is wanting the developers to concentrate on the AirPlay, Airport, Game Center, Graphics Drivers, and Safari. While the first Beta of the 10.8.3 came out in July 25th 2012, this is the longest period of testing that Apple has been performing for the Mac OS builds.
If our sources are to be believed, the previous one was the GM build, but the 10th beta was released to squash the file:// bug reported by a lot of people. Apple is also expected to roll out this update anytime this month to the end-users. We are already using 10.8.3 and there are no major bugs in the new update.