Developers already have what is likely the Golden Master – build number is 12A269, a 4.34 GB Mac App Store download. OS X 10.8 Mountain Lion will be a $19.99 upgrade which will hit the Mac App Store on launch day. But, there is already under two weeks left in July, and with last year’s launch pattern prime for repetition (launch announcement during the upcoming earnings call), we’d say a July 25th launch is increasingly likely. On the other hand, Apple often holds Tuesday overnights, so this July 24th overnight may simply be a coincidence, and Apple may not launch OS X Mountain Lion on the 25th.

Notably, some stores we’ve spoken to haven’t heard of any overnight…yet.

One employee tells us that it is basically just a few guys running around with the master image installing it on every Mac. This year, Mountain Lion isn’t being launched alongside hardware (last year new Minis and Airs launched with Lion) so there is less setup required and accordingly, we’re hearing that the overnights will be smaller. It appears that Apple may follow that same pattern this year. For OS X Lion’s launch last year, Apple announced the July 20th release at its July 19th Q3 2011 earnings announcement. This purported launch would be July 25th, a date that we speculated when Apple announced that its Q3 2012 earnings would be announced on the 24th. With OS X Mountain Lion launching “in July”, according to Apple, we believe that it is sensible to speculate that this overnight may point to a public launch the following day. We’ve heard a few whispers (3 and counting) that Apple Stores both in the United States and overseas have planned overnights for Tuesday, July 24th.

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