Mc and MB generationsI'm was pretty new to ipod touch 2nd and 3rd gen, so i didn't knew what is mb or mc. After some research I found out very simple information: MC is 3rd gen, and MB is 2nd generation ipod touch.
How to check your ipod touch modelGo 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.
DifferenceIf you wonder what difference between 2nd and 3rd gen - 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
Main difference is price. 3rd gen will cost you a bit more then 2nd.
Current ipod touch pricesMostly prices goes down, but in same cases they might get up because of various things. To check price you can use ebay or amazon - Check ipod touch current prices
Explaining video from youtube