Because of VSS 6.0 performance enhancements, you can perform a Get operation up to two times faster than in older versions of VSS.
In order to take advantage of VSS' Fast Get feature, you must first have your VSS Administrator run the DDUPD utility. See Using DDUPD to Take Advantage of Performance Enhancements for more information
When you do a Get, Check Out, Deploy or anything else that puts a copy of a file on your local drive, a vssver.scc file is created (or updated if one already exists) in your working folder. There's one vssver.scc for all the files in that folder. Vssver.scc contains information needed to identify the local file, so VSS can determine which files have and haven't changed.
Note If you delete the vssver.scc file, nothing will happen except that your new Get commands will be a bit slower and another vssver.scc file will be created. The vssver.scc file is ignored by the Project Difference command, and therefore will not show up as a file to Add to a VSS Project.