Q: How do I tell if my AppleTV is 1st 2nd or 3rd generation?

The 1st generation is much larger and a different color then the 2nd or 3rd.

See the differences here:

http://support.apple.com/manuals/#appletv

Really.

Then what about the color that I showed you.

Come On.

Black or Silver ?

Or look here:

http://support.apple.com/kb/HT5823

It's simple.

You can tell by the model number at the bottom.

3rd Gen woud have Model number on bottom: A1427 or A1469

2nd Gen would have Model number on bottom: A1378

1st Gen  would have Model number on bottom: A1218

More info: http://support.apple.com/kb/HT5823