From memory I don't believe that either Tablet or Media Centre Edition was ever available as a Retail version.
They were for OEM's to pre-install on suitable hardware.
You could check either the PID or the Volume Labels on these lists to see if you get a match: http://www.tacktech.com/display.cfm?ttid=342
It's possible to get the two disk CD MCE install onto one DVD (buy modifying the setup files) however I have never found a way to integrate SP3 on to the SP2 media supplied with MCE 2005. IT may not even be possible due to the WMP files included with MCE conflicting with those supplied in SP3.