Here are the features by which you can identify your iPod’s generation:
1st Generation iPod:
# A monochrome screen.
# A scroll wheel that physically turns.
# Control buttons placed around the scroll wheel
# Either 5 or 10GB capacity.
# A firewire connection.
# Only in white.
2nd Generation iPod:
# The scroll wheel replaced with a touch wheel (no physical movement), otherwise identical to generation 1
3rd Generation iPod:
# A monochrome screen.
# A touch wheel.
# Control buttons in a row directly below the screen.
# The fireWire port has a cover.
# The Dock Connector port was introduced.
# 10, 15, 20, 30, and 40 GB capacities.
4th Generation iPod:
# A monochrome screen (although some are colour)
# A touch wheel.
# The hold switch is on the top right side.
5th Generation iPod:
# Check if it plays movies. Known as the Video iPod or iPod Video, if your iPod plays movies it is a fifth generation iPod.
# A large “wide-screen” color display.
# A click wheel.
# Uses USB for synching.
# Only available in black and white.
80GB iPod 5.5:
# An 80GB hard drive.
# Look for a very large, wide-screen color display.
# A click Wheel.
# Can display photos and videos.
# Uses USB for synching.
# Only available in black and white.
# You can distinguish the new 80 gig version from the original 5th generation by the serial number. 80 gig versions have serial numbers ending in:V9K, V9P, V9M, V9R, V9L, V9N, V9Q, V9S, WU9, WUA, WUB, WUC, X3N.