It's Marcus. Add my msn: firstname.lastname@example.org
add my msn, email@example.com
No, I don't think that's it. If you can't figure it out, why don't you just let the client download the cache and go from there?
It's a value generated by the RS servers that serves as a sort of session key. If the private server you're trying to work with isn't using a very recent client build, you won't need to look for it. Otherwise, it'll probably be one of the applet parameters.