Good site I was about to post that but you beat me to the punch lol.... Another way to tell is that the older 160gb is thicker by a lot then the current 160gb..... The main reason Apple switched to the 80 then 120 is that the hard drives were thinner then when the thinner 160 came out Apple went to that.
----------
By the way I wouldn't sell the iPod if it's still in working order. As of right now no work on if apple is going to dicontune the Classic or upgrade it. With people's music collections growing and iCloud/Music match not being an option for every one (manly because people don't have unlimited data and would eat though their monthly cap). Just my thoughts. That is unless your music collection hasn't grown in the last ten years and you don't listen to music ever except your old CDs lol.......