Based on an entry in Apple's Radar bug reporting system, it looks like OS X 10.9 has undergone a far more comprehensive development phase than OS X 10.8 Mountain Lion, released last year. Details culled from a bug report that was sent using Apple's reporting system, called Radar, point to a number of likelihoods.

The entry pertains to an OS with a designated build number of 13A451. "13A" refers to what is most likely OS X 10.9, since OS X 10.8 had the designation of 12A and OS X 10.7 was 11A and so forth. The more interesting bit of information inferred from the build number, however, comes from the "451" part.

In Apple build designations, the number at the end stands for the number of builds that have been compiled and tested for that version of the OS. OS X 10.8 Mountain Lion, for instance, had gone through 269 builds before being publically released on July, 25 2012. Whenever it eventually rolls out, OS X 10.9 will have gone through at least 451 versions. What does this mean, though? There are a few possibilities.

First and foremost, the advanced build number suggests that OS X 10.9 is nearing a final release. It's more than probable that Apple will preview the new OS at WWDC 2013, which kicks off June 10. While likely, this would still be somewhat unusual given the fact that Apple has yet to share the latest iteration of its operating system with third-party developers. The high number of builds also suggests that OS X 10.9 will be a fairly major overhaul of the  operating system. It's not clear yet what the changes might be, but we probably won't have to wait more than a few days to find out.

Features like Notification Center have been creeping over from iOS to OS X so it will be interesting to see if that trend continues with the latest release, particularly given the rumored massive redesign in store for iOS 7, also expected to be unveiled at WWDC 2013.

An Apple Insider reader first spotted the build number and the site posted a story shorty thereafter.