It's only been four days since the Windows 10 Technical Preview was released to the public, however that doesn't mean the build that was issued with the Technical Preview is new. Windows 10 build 9841 was compiled on September 12, which was around three weeks ago. That's ancient in development time, so it's no surprise that build 9855 was recently compiled.
Thanks to the "preview builds" ability (which doesn't currently work) in the Windows 10 Technical Preview, users who are using the Technical Preview have managed to see some more recent builds of Windows 10. According to logs that appear when the operating system is attempting to connect to the update server, the operating system is seeing builds as new as a few days ago. Build 9855 was compiled on October 2nd, just two days ago.
For those who are keeping count (I am!), the full build string reads: 9855.0.141002-1432.winmain_CLIENTPRO_RET_x64fre_en-us.esd
The logs also reveal older builds too, spanning all the way back to June 2014 with build 9778. These builds would differ dramatically to that of the Windows 10 Technical Preview available today. It's still interesting to see how far back the Windows Update service can see builds though.
We'll be keeping a close eye on these builds as the number progresses. It shouldn't be long now before our first Technical Preview build is pushed out for the public, any guesses as to what build will get pushed?