I'm pretty sure that 1st gen nanos do
not support voice recording. And the difference is easy to tell:
1st gen: Mirror-shine black or white front, shiny metal back, rounded corners (when looking from the front), like this:
2nd gen: Matte-finish anodized aluminum body (all the way around, front and back) in silver, blue, green, pink, black, or red. Square corners looking from the front, rounded
sides instead, like this: