The short version: Is there a way to find the original operating system that shipped with my mac from within the operating system itself?

The long version:

I am trying to identify the version of OS X the originally shipped with my Mac. It is a Macbook pro from late 2008 15-inch. It is currently running 10.10.4 and it was originally running some version of Leopard but I'm not sure. How can I find out what version of Leopard it was originally running? It appears as though apple also provided an install disc for the original Leopard on the system but that disc doesn't have any printed information about what version of Leopard it is.

Thank you :)