Not possible to find.
See the sep empolyee TED G. comment
64-bit OSes will only allow you to install a 64-bit version os SEP, same with a 32-bit OS. You don't need to know which machines have what because when you assign a package to a group for migrating to the latest version the program is smart enough to know which package goes to which OS.
https://www-secure.symantec.com/connect/forums/how-can-you-tell-if-32-bit-or-64-bit-sep-installed
related forum
https://www-secure.symantec.com/connect/forums/compatability-issue