The WCF bits in the September CTP of the .NET Framework 3.0 were very, very close to the final bits that we ended up releasing and had the version number 3.0.4506.03

Between the September CTP and the RTM version, we only took a very small number of fixes into the product and did not increment the major build number (4506), but only the minor build numbers.

There is also a small discrepency between the minor build numbers for Vista and for the supported downlevel platforms (Windows XP and Windows Server 2003), because we took a number of downlevel-only setup fixes into the standalone .NET Framework 3.0 installer code that were not required for Vista. The product code in these two builds is identical.

The RTM WCF build numbers are:

Windows Vista (integrated .NET Framework 3.0): 3.0.4506.25
Windows XP and Windows Server 2003 (standalone .NET Framework 3.0): 3.0.4506.30