Many rumours have been floating about the internet recently, speculating about what build the Windows 8 RTM would receive. At one point people thought it was 8888, then 9200, it wasn't clear on which one it was. It appears today that 9200 has been confirmed as the RTM build number, with a complete build string.
9200.16384.win8_rtm.120725-1247 is the full final RTM build for Windows 8, which was compiled on the 25th July 2012 as a candidate. That build has been chosen by Microsoft employees over a long voting period, which means 9200 will be what hits the shelves later this year.