In the text below the engraving, look for the model number.
You can distinguish the iPod touch (3rd generation) from iPod touch (2nd generation) by looking at the back of the device.
IPod touch (3rd generation) features a 3.5-inch (diagonal) widescreen Multi-Touch display and 32 GB or 64 GB flash drive. Model number and date introduced: A1318: September 2009 IPod touch (4th generation) is available in white and black. IPod touch (4th generation) has an iSight camera and FaceTime HD camera. This model is available in silver and has a FaceTime HD camera. Model number and date introduced: A1509: May 2013 iPod touch (5th generation 16 GB, Mid 2013)
IPod touch (5th generation) is available in five colors.