You can determine the Premium AV version using the following steps:
1) On the server, go to the ../Program Files/Symantec/Scan Engine directory and locate "symcscan.exe".
2) Right click on the file and go to Properties.
3) Click the "version" tab to determine the version you are running.
(Note: Older versions of IMail AV were installed to a path of either drive:/symcscan or drive:/program files/symcscan.)