Members of a forum focused on Beta software that played around with RC Escrow Build 7601.17104 claim that there is a slipstream version of Windows 7 SP1 that's offered to select testers and members of the Technology Adoption Program through Microsoft Connect.
Of course, the software giant has yet to comment on any of the information on a potential RC Escrow Build for Windows 7 SP1.
Considering the info available in the wild, the full string for Windows 7 SP1 RC Escrow is 6.1.7601.17104.100921-1630, which means that the release was compiled on Sep'1st, 2010.
It appears that the release is time-bombed, and set to expire on 01.09.2011. Only the 32-bit (x86) Chinese version of Windows 7 SP1 RC Escrow Build 7601.17104 has so far been leaked.