Determining VCS Label Property

I would like to know the name of the VCS label property that is being passed to my build script.

Based on the current TeamCity documentation, I have been unable to determine the appropriate Label property.  While using CCNet, this was easily exposed as a parameter to my build via the property CCNetLabel.  Is there a similar property which I can utilize through TeamCity?

I am currently using TeamCity v. 5.1 Build 13130 EAP.

Thanks.