We have a branding solution developed and deployed to our 2010 environment.
I want to duplicate this solution so I can play around with it then deploy it along side the existing one.
I do not have the VS solution originally used by the developer but I have full access to the environment and Visual Studio.
Are you asking how to reverse engineer the code since you don't have it?
If that is what you are looking for, you are going to need the wsp file and a reverse engineering tool like the one that RedGate has.
There is more information here: http://social.technet.microsoft.com/wiki/contents/articles/17546.sharepoint-2010-reverse-engineering-sharepoint-wsp-packages.aspx
