Im pretty new to ipod touch 2nd and 3rd gen, so i didn't knew it till now... :D
So MC is 3rd gen, and MB is 2nd generation ipod touch.
if you go to Settings - General - About.
You will see your model. If it is mb, that means you have 2nd gen ipod touch, else if it is mc then it is 3rd...
If you wonder what difference between 2nd and 3rd gen, than... difference between mc and mb is:
-Faster CPU (should be roughly the same as the new 3GS processor)-OpenGL ES 2.0 graphics support-Apple inline remote support-VoiceOver (voice control)-Increase in capacity up to 64GB
P.S. Hope it will help, as it helped me... to make (^.^) _ \../